Autonomous coverage robot sensing

ABSTRACT

An autonomous coverage robot detection system includes an emitter configured to emit a directed beam, a detector configured to detect the directed beam and a controller configured to direct the robot in response to a signal detected by the detector. In some examples, the detection system detects a stasis condition of the robot. In some examples, the detection system detects a wall and can follow the wall in response to the detected signal.

CLAIM OF PRIORITY

This U.S. patent application is a continuation of and claims priority,under 35 U.S.C. § 120, to U.S. application Ser. No. 13/537,401, filedJun. 29, 2012, which is a continuation of and claims priority, under 35U.S.C. § 120, to U.S. application Ser. No. 13/314,398, filed Dec. 8,2011, which is a continuation of and claims priority, under 35 U.S.C. §120, to U.S. application Ser. No. 12/118,250, filed May 9, 2008, whichclaims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application60/938,699, filed on May 17, 2007 and U.S. Provisional Application60/917,065, filed on May 9, 2007. The disclosures of these priorapplications are considered part of the disclosure of this applicationand are hereby incorporated by reference in their entireties.

The contents of U.S. Pre-grant Publications 2008/00652565, 2007/0244610,and 2007/0016328, 2006/0200281, and 2003/0192144, and also U.S. Pat.Nos. 6,748,297 and 6,883,201 are hereby incorporated herein by referencein their entireties.

TECHNICAL FIELD

The disclosure relates to surface cleaning robots, such as robotsconfigured to perform autonomous cleaning tasks.

BACKGROUND

Wet cleaning of household surfaces has long been done manually using awet mop or sponge. The mop or sponge is dipped into a container filledwith a cleaning fluid to allow the mop or sponge to absorb an amount ofthe cleaning fluid. The mop or sponge is then moved over the surface toapply a cleaning fluid onto the surface. The cleaning fluid interactswith contaminants on the surface and may dissolve or otherwise emulsifycontaminants into the cleaning fluid. The cleaning fluid is thereforetransformed into a waste liquid that includes the cleaning fluid andcontaminants held in suspension within the cleaning fluid. Thereafter,the sponge or mop is used to absorb the waste liquid from the surface.While clean water is somewhat effective for use as a cleaning fluidapplied to household surfaces, most cleaning is done with a cleaningfluid that is a mixture of clean water and soap or detergent that reactswith contaminants to emulsify the contaminants into the water. Inaddition, it is known to clean household surfaces with water anddetergent mixed with other agents such as a solvent, a fragrance, adisinfectant, a drying agent, abrasive particulates and the like toincrease the effectiveness of the cleaning process.

The sponge or mop may also be used as a scrubbing element for scrubbingthe floor surface, and especially in areas where contaminants areparticularly difficult to remove from the household surface. Thescrubbing action serves to agitate the cleaning fluid for mixing withcontaminants as well as to apply a friction force for looseningcontaminants from the floor surface. Agitation enhances the dissolvingand emulsifying action of the cleaning fluid and the friction forcehelps to break bonds between the surface and contaminants.

After cleaning an area of the floor surface, the waste liquid must berinsed from the mop or sponge. This is typically done by dipping the mopor sponge back into the container filled with cleaning fluid. Therinsing step contaminates the cleaning fluid with waste liquid and thecleaning fluid becomes more contaminated each time the mop or sponge isrinsed. As a result, the effectiveness of the cleaning fluiddeteriorates as more of the floor surface area is cleaned.

Some manual floor cleaning devices have a handle with a cleaning fluidsupply container supported on the handle and a scrubbing sponge at oneend of the handle. These devices include a cleaning fluid dispensingnozzle supported on the handle for spraying cleaning fluid onto thefloor. These devices also include a mechanical device for wringing wasteliquid out of the scrubbing sponge and into a waste container.

Manual methods of cleaning floors can be labor intensive and timeconsuming. Thus, in many large buildings, such as hospitals, largeretail stores, cafeterias, and the like, floors are wet cleaned on adaily or nightly basis. Industrial floor cleaning “robots” capable ofwet cleaning floors have been developed. To implement wet cleaningtechniques required in large industrial areas, these robots aretypically large, costly, and complex. These robots have a drive assemblythat provides a motive force to autonomously move the wet cleaningdevice along a cleaning path. However, because these industrial-sizedwet cleaning devices weigh hundreds of pounds, these devices are usuallyattended by an operator. For example, an operator can turn off thedevice and, thus, avoid significant damage that can arise in the eventof a sensor failure or an unanticipated control variable. As anotherexample, an operator can assist in moving the wet cleaning device tophysically escape or navigate among confined areas or obstacles.

SUMMARY

Presently disclosed is an autonomous robot for treating surfaces, suchas floors and countertops, which has a form factor that facilitatescleaning in tightly dimensioned spaces, such as those found in manyhouseholds. In one example, the robot may include a weight distributionthat remains substantially constant throughout the cleaning process, theweight distributed between a cleaning element, a squeegee, and drivewheels. The weight distribution can provide sufficient pressure to thewetting element and the squeegee while allowing sufficient thrust for tobe applied at drive wheels. As an advantage, the robot can have a smallvolume required to navigate in tightly dimensioned spaces while having aweight distribution configured for wet-cleaning a surface.

In one aspect, a surface treatment robot includes a chassis havingforward and rear ends and a drive system carried by the chassis. Thedrive system is configured to maneuver the robot over a cleaning surfaceand includes right and left differentially driven wheels. The robotincludes a vacuum assembly carried by the chassis. The vacuum assemblyincludes a collection region that engages the cleaning surface and asuction region in fluid communication with the collection region. Thesuction region is configured to suction waste from the cleaning surfacethrough the collection region. The robot includes a collection volumecarried by the chassis and in fluid communication with the vacuumassembly for collecting waste removed by the vacuum assembly. The robotincludes a supply volume carried by the chassis and configured to hold acleaning liquid. An applicator is carried by the chassis and is in fluidcommunication with the supply volume. The applicator is configured todispense the cleaning liquid onto the cleaning surface substantiallynear the forward end of the chassis. The robot includes a wettingelement carried by the chassis and engaging the cleaning surface todistribute the cleaning liquid along at least a portion of the cleaningsurface when the robot is driven in a forward direction. The wettingelement is arranged substantially forward of a transverse axis definedby the right and left driven wheels, and the wetting element slidablysupports at least about ten percent of the mass of the robot above thecleaning surface.

Implementations of this aspect of the disclosure may include one or moreof the following features. In some implementations, the collectionregion of the vacuum assembly is arranged substantially rearward of thetransverse axis defined by the right and left drive wheels, and thevacuum assembly slidably supports at least about twenty percent of themass of the robot above the cleaning surface. In certainimplementations, a forward portion of the collection region of thevacuum assembly is configured to pass a point on the cleaning surfaceabout 0.25 s to about 0.6 s after a forward portion of the applicatorhas passed the point on the cleaning surface when the robot is driven ata maximum speed in the forward direction.

In some implementations, the robot includes a navigation system incommunication with the drive system and configured to navigate therobot. The vacuum assembly is configured to collect a portion of thecleaning liquid dispensed onto the cleaning surface and the navigationsystem is configured to navigate the robot to return to collect thecleaning liquid remaining on the surface. In certain implementations,the navigation system is configured to navigate the robot along apseudo-random path to return to collect the cleaning liquid remaining onthe surface.

In some implementations, the collection region of the vacuum assemblyincludes a squeegee and a vacuum chamber. The squeegee is attached tothe chassis and formed with a longitudinal ridge disposed proximate tothe cleaning surface and extending across a cleaning width for providinga liquid collection volume at a forward edge of the ridge. The vacuumchamber is partially formed by the squeegee, and the vacuum chamber isdisposed proximate to the longitudinal ridge, extending across thecleaning width. The vacuum chamber is in fluid communication with theliquid collection volume by a plurality of suction ports defined by thesqueegee, substantially above the longitudinal ridge.

In some implementations, the drive system is configured to maneuver therobot within a volume of less than about 3 L. In certainimplementations, the supply volume is configured to hold about 600 mL orgreater of cleaning liquid.

In some implementations, the drive system is configured to providebetween about 100 grams-force and about 700 grams-force at each wheel topropel the robot at a maximum forward rate of about 200 mm/s to about400 mm/s. In certain implementations, the center of gravity of the robotis substantially along a transverse axis defined by the right and leftdifferentially driven wheels.

In some implementations, the robot includes an extension element carriedby the chassis and extending transversely from the chassis. Theextension element is configured to guide debris toward the chassis. Incertain implementations, the extension element includes a spring detentconfigured to allow the extension element to flex upon contact with anobstacle and to return to a substantially original position upondisengagement from the obstacle. In some implementations, the extensionelement is in fluid communication with the vacuum assembly andconfigured to suction debris toward the vacuum assembly.

In another aspect a surface treatment robot includes a chassis havingforward and rear ends and a drive system carried by the chassis andconfigured to maneuver the robot over a cleaning surface. The drivesystem includes right and left differentially driven wheels. The robotincludes a vacuum assembly carried by the chassis and including acollection region and a suction region. The collection region engagesthe cleaning surface and the suction region is in fluid communicationwith the collection region. The suction region is configured to suctionwaste from the cleaning surface through the collection region. The robotincludes a collection volume carried by the chassis and in fluidcommunication with the vacuum assembly for collecting waste removed bythe vacuum assembly. The robot includes a supply volume carried by thechassis and configured to hold a cleaning liquid. An applicator iscarried by the chassis and in fluid communication with the supplyvolume. The applicator is configured to dispense the cleaning liquidonto the cleaning surface substantially near the forward end of thechassis. The supply volume and the collection volume are configured tomaintain a substantially constant center of gravity along a transverseaxis defined by the right and left differentially driven wheels while atleast about 25 percent of the total volume of the robot shifts fromcleaning liquid in the supply volume to waste in the collection volumeas cleaning liquid is dispensed from the applicator and waste iscollected by the vacuum assembly.

In some implementations, at least a portion of the supply volumeincludes a bladder disposed substantially within the collection volume.The bladder is expandable to hold a volume of cleaning fluid of at leastabout 25 percent of the total volume of the robot, and the bladder iscollapsible to allow the collection volume to hold a volume of waste ofat least about 25 percent of the total volume of the robot.

In some implementations, the wetting element has a substantially arcuateshape and includes bristles extending from the wetting element to engagethe cleaning surface. The bristles are configured to deformsubstantially separately from one another to dissipate a force createdwhen the wetting element contacts an obstacle as the robot is driven.

In some implementations, the collection region of the vacuum assemblyhas a transverse dimension substantially equal to a transverse dimensionof the wetting element, and the right and left differentially drivenwheels define a transverse dimension less than or equal to thetransverse dimension of the wetting element.

In some implementations, the suction region of the vacuum assemblyincludes a fan and an intake conduit in fluid communication with the fanand in fluid communication with the vacuum chamber. The fan isconfigured to draw air from the vacuum chamber through the intakeconduit to generate a negative air pressure within the vacuum chamberfor drawing waste liquid from the collection region into the vacuumchamber. At least a portion of the intake conduit is arranged about 90degrees relative to the direction of flow of the waste liquid into thevacuum chamber to block substantial flow of waste liquid into the fan.

In certain implementations, the supply volume defines a first port andthe collection volume defines a second port. The first port is arrangedsubstantially opposite the second port to allow the robot to remain insubstantially the same orientation when cleaning liquid is added to thesupply volume as when waste is emptied from the collection volume. Insome implementations, the robot includes a bumper carried by the chassisand arranged substantially along the front end of the chassis. Thebumper defines an opening providing access to the first port of thesupply volume.

In another aspect, an autonomous coverage robot includes a body havingforward and rear ends, a perimeter, and a top region. The robot includesa drive system carried by the body and configured to maneuver the robotover a cleaning surface, the drive system comprising right and leftdifferentially driven wheels. The robot includes an optical receivercarried by the body substantially below the top region and substantiallyforward of the transverse axis defined by the right and leftdifferentially driven wheels. The robot includes a signal channeler inoptical communication with the optical receiver. The signal channeler isarranged along the top region of the body and extends substantiallyaround the entire perimeter of the body. The signal channeler isconfigured to receive an optical signal from a remote transmitter insubstantially any direction around the perimeter of the body. The signalchanneler is internally reflective to direct the optical signal towardthe receiver, and the drive system is configured to alter a headingsetting in response to the optical signal received by the receiver.

In some implementations, the robot includes a collection volume carriedby the body for collecting waste removed from the surface by the robot.The signal channeler forms at least a portion of the top surface of thecollection volume.

In certain implementations, at least a portion of the signal channeleris formed of a material having an index of refraction of about 1.4 orgreater to allow substantially total internal reflection within thesignal channeler. In some implementations, the signal channeler includesa first mirror disposed along a first surface and a second mirrordisposed along a second surface, opposite the first surface. The firstmirror and the second mirror are configured to internally reflect lightwithin the signal channeler.

In another aspect, an autonomous robot includes a chassis and abiased-to-drop suspension system coupled to the chassis. Thebiased-to-drop suspension system has a top position and a bottomposition. The robot includes a vacuum assembly carried by the chassisand configured to suction waste from the cleaning surface. A collectionvolume is carried by the chassis and in fluid communication with thevacuum assembly for collecting waste suctioned by the vacuum assembly.The robot includes a seal movable from an open position to a closedposition to interrupt at least a portion of the fluid communicationbetween the vacuum assembly and the collection volume. The seal iscoupled to the suspension system and configured to move from the openposition to the closed position when the biased-to-drop suspensionsystem moves from the top position to the bottom position.

In some implementations, the vacuum assembly includes a fan and the sealis configured to interrupt at least a portion of the fluid communicationbetween the fan and the collection volume.

In another aspect, a robot stasis detection system includes a bodyconfigured to move over a surface and a stasis sensor carried by thebody. The stasis sensor includes an optical emitter configured to emit adirected beam and a photon detector operable to detect the directedbeam. The stasis sensor includes an object positioned between thedirected beam and the photon detector to block substantial opticalcommunication between the optical emitter and the photon detector. Theobject is movable in response to a motion sequence of the body to allowsubstantial optical communication between the optical emitter and thephoton detector. The robot stasis detection system includes a controllerin electrical communication with the stasis sensor and configureddetermine a stasis condition based at least in part on a level ofoptical communication between the optical emitter and the photondetector.

In some implementations, the controller is configured to maneuver thebody to cause the motion sequence of the body. In certainimplementations, the robot stasis detection system includes two drivenwheels carried by the body, and the controller is configured drive thetwo wheels differentially to cause the motion sequence of the body. Incertain implementations, the robot stasis detection system includes awetting element carried by the body and in contact with the surface. Thewetting element is configured to spread a cleaning liquid on the surfaceduring the motion sequence of the body.

In another aspect, a method of detecting stasis of an autonomous robotincludes emitting a directed beam from an optical emitter carried on therobot. The method includes controlling a drive system of the robot toprovide a motion sequence of the robot. As an object carried on therobot moves in response to the motion sequence of the robot, the methodincludes detecting the directed beam at a photon detector carried on therobot. A stasis condition of the robot is determined based at least inpart on a level of optical communication between the optical emitter andthe photon detector.

In some implementations, controlling the drive system of the robotincludes differentially driving two wheels carried on the robot toprovide the motion sequence of the robot. In certain implementations,the robot is configured to carry a cleaning element in contact with asurface and the motion sequence of the robot is part of a cleaningroutine of the robot. In some implementations, the robot defines acenter vertical axis and controlling a drive system of the robot toprovide a motion sequence of the robot comprises a sequence of drivecommands configured to rotate the robot about the center vertical axis.

In another aspect, a method of detecting stasis of an autonomous robotincludes maneuvering a robot over a surface and, from an optical emittercarried on the robot, emitting a directed beam from the optical emitter.At a photon detector carried on the robot, the method includes detectinga reflection of the directed beam from the surface. The method includesdetermining a stasis condition of the robot based at least in part onvariations in strength of the reflection detected by the photondetector.

In some implementations, maneuvering the robot over the surface includesdifferentially driving two wheels to move a passive cleaning element,carried by the robot, over the surface. In certain implementations,emitting the directed beam toward the surface includes emitting thedirected beam toward the surface forward of the passive cleaningelement. In some implementations, the method includes comparing thedetermined stasis condition of the robot with a second stasis conditiondetermined by a second sensor carried by the robot. In certainimplementations, maneuvering the robot over a surface includes movingthe robot over the surface at a forward rate of about 200 m/s to about400 m/s. In some implementations, the method includes determining thepresence of a cliff forward of the robot based on the strength of thesignal detected by the photon detector.

In another aspect, a robot wall detection system includes a bodyconfigured to move over a surface and a sensor carried by the body fordetecting the presence of a wall. The sensor includes an emitter whichemits a directed beam having a defined field of emission toward a wallin a substantially forward direction of the body. The sensor includes adetector having a defined field of view extending toward the wall in asubstantially forward direction of the robot. The defined field of viewis near-parallel to the defined field of emission and intersects thedefined field of emission at a finite region substantially forward ofthe sensor. A circuit in communication with the detector controls thedistance between the body and the wall.

In some implementations, the body is configured to move the detectorforward at about 200 mm/s to about 400 mm/s. In certain implementations,the controller is configured to maintain a constant analog value of thedetector to move the body at a substantially constant distance from thewall. In some implementations, the defined field of emission is arrangedrelative to the defined field of view to provide a substantially linearrelationship between distance from the wall and strength of the signaldetected by the detector. In certain implementations, an included anglebetween the defined field of emission and the defined field of view isabout 10 degrees to about 30 degrees.

Other aspects, features, and advantages will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic block diagram showing the interrelationship ofsubsystems of an autonomous cleaning robot.

FIG. 2 is a perspective view of an autonomous cleaning robot.

FIG. 3 is a bottom view of the autonomous cleaning robot of FIG. 1.

FIG. 4 is a side view of the autonomous cleaning robot of FIG. 1.

FIG. 5 is a front view of the autonomous cleaning robot of FIG. 1.

FIG. 6 is a rear view of the autonomous cleaning robot of FIG. 1.

FIG. 7 is an exploded perspective view of the autonomous cleaning robotof FIG. 1 (shown the user interface removed).

FIG. 8 is a schematic representation of a liquid applicator module ofthe autonomous cleaning robot of FIG. 1.

FIG. 9 is a perspective view of a wetting element of the autonomouscleaning robot of FIG. 1.

FIG. 10 is a top view of a wetting element of an autonomous cleaningrobot.

FIG. 11 is a perspective view of an active brush element.

FIG. 12 is a top view of an autonomous cleaning robot.

FIG. 13 is a schematic representation of a vacuum module of anautonomous cleaning robot.

FIG. 14 is a perspective view of a portion of the vacuum module of anautonomous cleaning robot.

FIG. 15A-B is a schematic representation of an active sealing system ofan autonomous cleaning robot.

FIG. 16 is an exploded perspective view of a fan of an autonomouscleaning robot.

FIG. 17 is a perspective view of a squeegee of the autonomous cleaningrobot of FIG. 1.

FIG. 18 is a side view of the squeegee of the autonomous cleaning robotof FIG. 1.

FIG. 19 is a bottom view of the squeegee of the autonomous cleaningrobot of FIG. 1.

FIG. 20 is an exploded perspective view of a wheel of the autonomouscleaning robot of FIG. 1.

FIG. 21 is a perspective view of a wire seal of an autonomous cleaningrobot.

FIG. 22 is an exploded perspective view of a signal channeler andomni-directional receiver of an autonomous cleaning robot.

FIG. 23A is a partial top cross-sectional view of a wall follower sensormounted on a bumper of the autonomous cleaning robot of FIG. 1.

FIG. 23B is a schematic representation of a wall follower sensor of anautonomous cleaning robot.

FIG. 24 is a flow chart depicting steps associated with the logic of anautonomous cleaning robot including a wall follower.

FIG. 25 is a perspective view of a bump sensor of an autonomous cleaningrobot.

FIG. 26 is a cross sectional view of the bump sensor of FIG. 25 takenalong the line 26-26.

FIG. 27 is a rear view of the bumper of the autonomous cleaning robot ofFIG. 1.

FIG. 28 is a schematic representation of a bumper in alignment withwheels of an autonomous cleaning robot.

FIG. 29 is a schematic representation of a cliff sensor of an autonomouscleaning robot.

FIG. 30 is a flow chart depicting steps associated with the logic of anautonomous cleaning robot including a cliff detector.

FIG. 31 is a side view of the chassis of the autonomous cleaning robotof FIG. 1 with a stasis sensor mounted to the chassis.

FIG. 32 is an exploded perspective view of a stasis sensor of theautonomous cleaning robot of FIG. 1.

FIG. 33 is a top view of a wiggle sensor of an autonomous cleaningrobot.

DETAILED DESCRIPTION

An autonomous robot may be designed to clean flooring. For example, theautonomous robot may vacuum carpeted or hard-surfaces and wash floorsvia liquid-assisted washing and/or wiping and/or electrostatic wiping oftile, vinyl or other such surfaces. U.S. application Ser. No. 11/359,961by Ziegler et al. entitled AUTONOMOUS SURFACE CLEANING ROBOT FOR WET ANDDRY CLEANING the disclosure of which is herein incorporated by referencein its entirety, discloses an autonomous cleaning robot.

An autonomous robot is movably supported on a surface and is used toclean the surface while traversing the surface. The robot can wet cleanthe surface by applying a cleaning liquid to the surface, spreading(e.g., smearing, scrubbing) the cleaning liquid on the surface, andcollecting the waste (e.g., substantially all of the cleaning liquid anddebris mixed therein) from the surface. As compared to comparable-sizedautonomous dry cleaning robots, an autonomous wet cleaning robot canremove more debris from a surface.

FIG. 1 is a schematic block diagram showing the interrelationship ofsubsystems of an autonomous cleaning robot. A controller 1000 is poweredby a powered by a power module 1200 and receives inputs from a sensormodule 1100 and an interface module 1700. The controller 1000 combinesthe inputs from the sensor module 1100 with information (e.g.,behaviors) preprogrammed on the controller 1000 to control a liquidstorage module 1500, a liquid applicator module 1400, and a vacuummodule 1300 (e.g., a wet-dry vacuum module) while also controlling atransport drive 1600 to maneuver the autonomous cleaning robot across acleaning surface (hereinafter referred to as a “surface”).

A controller 1000 (e.g., a controller on the robot) controls theautonomous movement of the robot across the surface by directing motionof the drive wheels that are used to propel the robot across thesurface. The controller 1000 can redirect the motion of the robot inresponse to any of various different signals from sensors (e.g., sensorscarried on the robot, a navigation beacon). Additionally oralternatively, the controller can direct the robot across the surface ina substantially random pattern to improve the cleaning coverage providedby the robot.

Prior to the cleaning operation, cleaning liquid can be added to theliquid storage module 1500 via an external source of cleaning liquid.The robot can then be set on a surface to be cleaned, and cleaning canbe initiated through an interface module 1700 (e.g., a user interfacecarried by the robot). The controller 1000 controls the transport drive1600 to maneuver the robot in a desired pattern across the surface. Asthe controller 1000 controls the movements of the robot across thesurface, the controller also controls a liquid applicator module 1400 tosupply cleaning liquid to the surface and a vacuum module 1300 tocollect waste from the surface.

After the cleaning operation is complete (e.g., after all of thecleaning liquid has been dispensed from the robot, after the robot hascompleted a routine, after an elapsed period of time), waste can beremoved from the robot. The robot is lightweight and has a compact formfactor that each facilitate, for example, handling of the robot suchthat the robot can be moved to another area to be cleaned or put instorage until a subsequent use. The robot is substantially sealable(e.g., passively sealable, actively sealable) to minimize spillage ofcleaning liquid and/or waste from the robot while the robot is in use orwhile the robot is being handled.

Referring to FIGS. 2-6, a robot 10 includes a chassis 100 carrying abaseplate 200, a bumper 300, a user interface 400, and wheel modules500, 501. Wheel modules 500, 501 are substantially opposed along atransverse axis defined by the chassis 100. Baseplate 200 is carried ona substantially bottom portion of chassis 100 and at least partiallysupports a front portion of the chassis 100 above the surface. As wheelmodules 500, 501 propel the robot 10 across the surface during acleaning routine, the baseplate 200 makes slidable contact with thesurface and wet-vacuums the surface by delivering cleaning liquid to thesurface, spreading the cleaning liquid on the surface, and collectingwaste from the surface and into the volume defined by the robot 10. Auser interface 400 is carried on a substantially top portion of thechassis 100 and configured to receive one or more user commands and/ordisplay a status of the robot 10. The user interface 400 is incommunication with a controller (described in detail below) carried bythe robot 10 such that one or more commands to the user interface 400can initiate a cleaning routine to be executed by the robot 10. A bumper300 is carried on a forward portion of the chassis 100 and configured todetect one or more events in the path of the robot 10 (e.g., as wheelmodules 500, 501 propel the robot 10 across a surface during a cleaningroutine). As described in detail below, the robot 10 can respond toevents (e.g., obstacles, cliffs, walls) detected by the bumper 300 bycontrolling wheel modules 500, 501 to maneuver the robot 10 in responseto the event (e.g., away from the event). While some sensors aredescribed herein as being arranged on the bumper, these sensors canadditionally or alternatively be arranged at any of various differentpositions on the robot 10.

The robot 10 stores cleaning fluid and waste and, thus, substantiallythe entire electrical system is fluid-sealed and/or isolated fromcleaning liquid and/or waste stored on the robot 10. Examples of sealingthat can be used to separate electrical components of the robot 10 fromthe cleaning liquid and/or waste include covers, plastic or resinmodules, potting, shrink fit, gaskets, or the like. Any and all elementsdescribed herein as a circuit board, PCB, detector, or sensor can besealed using any of various different methods.

The robot 10 can move across a surface through any of various differentcombinations of movements relative to three mutually perpendicular axesdefined by the chassis: a central vertical axis 20, a fore-aft axis 22and a transverse axis 24. The forward travel direction along thefore-aft axis 22 is designated F (sometimes referred to hereinafter as“forward”), and the aft travel direction along the fore-aft axis 22 isdesignated A (sometimes referred to hereinafter as “rearward”). Thetransverse axis extends between a right side, designated R, and a leftside, designated L, of the robot 10 substantially along an axis definedby center points of wheel modules 500, 501. In subsequent figures, the Rand L directions remain consistent with the top view, but may bereversed on the printed page.

In use, a user opens a fill door 304 disposed along the bumper 300 andadds cleaning fluid to the volume within the robot 10. After addingcleaning fluid to the robot 10, the user then closes the fill door 304such that the fill door 304 forms a substantially water-tight seal withthe bumper 300 or, in some implementations, with a port extendingthrough the bumper 300. The user then sets the robot 10 on a surface tobe cleaned and initiates cleaning by entering one or more commands onthe user interface 400.

The controller carried by the robot 10 directs motion of the wheelmodules 500, 501. The controller can control the rotational speed anddirection of each wheel module 500, 501 independently such that thecontroller can maneuver the robot 10 in any of various differentdirections. For example, the controller can maneuver the robot 10 in theforward, reverse, right, and left directions. For example, as the robot10 moves substantially along the fore-aft axis 22, the robot 10 can makerepeated alternating right and left turns such that the robot 10 rotatesback and forth around the center vertical axis 20 (hereinafter referredto as a wiggle motion). As described in detail below, such a wigglemotion of the robot 10 can allow the robot 10 to operate as a scrubberduring the cleaning operation. As also described in detail below, awiggle motion of the robot 10 can be used by the controller to detectstasis of the robot 10. Additionally or alternatively, the controllercan maneuver the robot 10 to rotate substantially in place such that,for example, the robot can maneuver out of a corner or away from anobstacle. In some implementations, the controller directs the robot 10over a substantially random (e.g., pseudo-random) path traversing thesurface to be cleaned. As described in detail below, the controller isresponsive to any of various different sensors (e.g., bump sensors,proximity sensors, walls, stasis conditions, and cliffs) disposed aboutthe robot 10. The controller can redirect wheel modules 500, 501 inresponse to signals from the sensors such that the robot 10 wet vacuumsthe surface while avoiding obstacles and clutter. If the robot 10becomes stuck or entangled during use, the controller is configured todirect wheel modules 500, 501 through a series of escape behaviors suchthat the robot 10 can resume normal cleaning of the surface.

The robot 10 is generally advanced in a forward direction duringcleaning operations. The robot 10 is generally not advanced in the aftdirection during cleaning operations but may be advanced in the aftdirection to avoid an object or maneuver out of a corner or the like.Cleaning operation can continue or be suspended during aft transport.

During wet vacuuming, cleaning liquid can be dispensed to the surfacethrough an applicator mounted directly to the chassis (e.g., to be usedas an attachment point for the bumper and/or to conceal wires).Additionally or alternatively, the cleaning liquid can be dispensed tothe surface through an applicator mounted to a baseplate. For example,cleaning liquid can be dispensed through trough 202 carried on thebaseplate 200, along a substantially forward portion of the robot 10.The trough 202 defines injection orifices 210 configured along thelength of the trough 202 to produce a spray pattern of cleaning fluid.As described in detail below, a pump upstream of the trough 202 forcescleaning liquid through injection orifices 210 to deliver cleaningliquid to the surface. In some implementations, injection orifices 210are substantially equally spaces long the length of the trough 202 toproduce a substantially uniform spray pattern of cleaning liquid on thesurface. In some embodiments, the injection orifices 210 are configuredto allow cleaning liquid to drip from the injection orifices 210.

A wetting element 204 is carried on the baseplate 200, substantiallyrearward of the trough 202. Ends of the wetting element 204 extend in atransverse direction substantially the entire width (e.g., diameter) ofthe robot 10. In use, the wetting element 204 slidably contacts thesurface to support a forward portion of the robot 10 above the cleaningsurface. As the robot 10 moves in a substantially forward direction, thesliding contact between the wetting element 204 and the surface spreadsthe cleaning liquid on the surface. In some implementations, a secondwetting element 206 is carried on the baseplate 200, substantiallyrearward of the wetting element 204 to further spread and/or agitate thecleaning liquid on the surface.

As the robot continues to move forward, wheel modules 500, 501 passthrough the cleaning liquid spread on the surface. A combination ofweight distribution (e.g., drag) of the robot 10, material selection forthe tires of the wheel modules 500, 501, and a biased-to-drop suspensionsystem improve the traction of wheel modules 500, 501 through thecleaning liquid such that wheel modules 500, 501 can pass over thecleaning liquid without substantial slipping.

A squeegee 208 is carried on the baseplate 200 and, during use, extendsfrom the baseplate 200 to movably contact the surface. The squeegee 208is positioned substantially rearward of the wheel modules 500, 501. Ascompared to a robot including a squeegee in a more forward position,such rearward positioning of the squeegee 208 can increase the dwelltime of the cleaning liquid on the surface and, thus, increase theeffectiveness of the cleaning operation. Additionally or alternatively,such rearward positioning of the squeegee 208 can reduce rearwardtipping of the robot 10 in response to thrust created by the wheelmodules 500, 501 propelling the robot 10 in a forward direction.

As described in detail below, the movable contact between the squeegee208 acts to lift waste (e.g., a mixture of cleaning liquid and debris)from the cleaning surface as the robot 10 is propelled in a forwarddirection. The squeegee 208 is configured to pool the wastesubstantially near suction apertures 212 defined by the squeegee 208. Avacuum assembly carried by the robot 10 suctions the waste from thecleaning surface and into the robot 10, leaving behind a wet vacuumedsurface.

After all of the cleaning fluid has been dispensed from the robot 10,the controller stops movement of the robot 10 and provides an alert(e.g., a visual alert or an audible alert) to the user via the userinterface 400. The user can then open an empty door 104 to expose awaste port defined by the waste collection volume remove collected wastefrom the robot 10. Because the fill door 304 and the empty door 104 aredisposed along substantially opposite sides of the chassis, the filldoor 304 and the empty door 104 can be opened simultaneously to allowwaste to drain out of the robot 10 while cleaning liquid is added to therobot 10.

If the user wishes to move the robot 10 between uses, the user may move(e.g., rotate) a handle 401 away from the chassis 100 and lift the robot10 using the handle 401. The handle 401 pivots about a transverse axis(e.g., a center transverse axis) including the center of gravity of therobot 10 such that the handle 401 can be used to carry the robot 10substantially like a pail. The robot 10 includes a passive sealingsystem and/or an active sealing system such that the robot 10 remainssubstantially water-tight during transport. An active and/or passivesealing system can reduce the escape of waste and/or cleaning fluid fromthe robot 10 as the robot 10 is moved from one area to another.Accordingly, the robot 10 can be moved and stored with little risk ofcreating hazardous, slippery conditions resulting from liquid drippingfrom the robot. Additionally or alternatively, the robot 10 can be movedand stored with little risk of dripping liquid on the user or onsurfaces that have already been cleaned.

After moving the robot 10, the user can position the handle 401 backinto a position substantially flush with the top portion of the robot toreduce the potential for the handle 401 becoming entangled with anobject while the robot 10 is in use. In some implementations, the handle401 includes a magnetized portion that biases the handle 401 toward aposition flush with the top portion of the robot. In someimplementations, the handle 401 includes a spring that biases the handle401 toward a position substantially flush with the top portion of therobot 10.

Between uses, the user can recharge a power supply carried on-board therobot 10. To charge the power supply, the user can open a charge portdoor 106 on a back portion of the chassis 100. With the charge port door106 open, the user can connect a wall charger to a charge port behindthe charge port door 106. The wall charger is configured to plug into astandard household electrical outlet. During the charging process, oneor more indicators (e.g., visual indicators, audible indicators) on theuser interface 400 can alert the user to the state of charge of thepower supply. Once the power supply has been recharged (e.g., asindicated by the user interface 400), the user can disconnect the robot10 from the wall charger and close the charge port door 106. The chargeport door 106 forms a substantially water-tight seal with the chassis100 such that the charge port remains substantially free of liquid whenthe charge port door 106 is closed. In some implementations, the powersupply is removed from the robot 10 and charged separately from therobot 10. In some implementations, the power supply is removed andreplaced with a new power supply. In some implementations, the robot 10is recharged through inductive coupling between the robot 10 and aninductive transmitter. Such inductive coupling can improve the safety ofthe robot 10 by reducing the need for physical access to electroniccomponents of the robot 10.

Form Factor

The chassis 100, baseplate 200, bumper 300, user interface 400, andwheel modules 500, 501 fit together such that robot 10 has asubstantially cylindrical shape with a top surface and a bottom surfacethat is substantially parallel to and opposite the top surface. Such asubstantially cylindrical shape can reduce the potential for the robot10 to become entangled (e.g., snagged) and/or break on obstacles as therobot 10 traverses a surface.

In some implementations, the substantially cylindrical shape of therobot 10 has a form factor that allows a user to lift and manipulate therobot 10 in a manner similar to the manipulation of a typical canteencarried by hikers. For example, a user can fill the robot 10 withcleaning liquid by placing the robot 10 under a typical bathroom orkitchen faucet. With the robot 10 in the same orientation used to fillthe robot with cleaning liquid, the robot can be emptied into thebathroom or kitchen sink. The robot 10 includes a front face 302 and aback face 102, each of which are substantially flat and configured tobalance the robot 10 on end. For example, a user can place back face 102on a substantially flat surface (e.g., a countertop, bottom of a kitchensink, bottom of a bathtub) such that the robot 10 is balanced on thecountertop with front face 302 facing upward toward the user. Such anorientation can allow a user to fill the robot 10 with cleaning liquidwithout holding the robot. Additionally or alternatively, a user canplace front face 302 on a substantially flat surface to allow a user tomore easily access components of the robot 10 (e.g., a batterycompartment, a charging port).

The robot 10 performs cleaning operations in tightly dimensioned areas.In some implementations, the robot 10 can have a compact form factor foravoiding clutter or obstacles while wet-vacuuming a surface. Forexample, the robot 10 can be dimensioned to navigate household doorways,under toe kicks, and under many typical chairs, tables, portableislands, and stools, and behind and beside some toilets, sink stands,and other porcelain fixtures. In certain implementations, the overallheight of the robot 10 is less than a standard height of a toe-kickpanel of a standard North American bathroom vanity. For example, theoverall height of the robot 10 can be less than about 18 centimeters(e.g., about 15 centimeters, about 12 centimeters, about 9 centimeters).In certain implementations, the overall diameter of the robot 10 isapproximately equal to the standard distance between the base of aninstalled toilet and a bathroom wall. As compared to larger diameterrobots, such a diameter of the robot 10 can improve cleaning around thebase of a toilet, e.g., substantially between the toilet and the wall.For example, the overall diameter of the robot 10 can be less than about26 centimeters (e.g., about 20 centimeters, about 15 centimeters, about10 centimeters). In certain implementations, the wheel modules 500, 501are configured to maneuver the robot 10 in such tightly dimensionedspaces (e.g., in a volume of less than about 3 L).

While the robot 10 is described as having a substantially cylindricalshape in the range of dimensions described above, the robot 10 can haveother cross-sectional diameter and height dimensions, as well as othercross-sectional shapes (e.g. square, rectangular and triangular, andvolumetric shapes, e.g. cube, bar, and pyramidal) to facilitate wetcleaning narrow or hard-to-reach surfaces.

Within a given size envelope, larger volumes of cleaning liquid can bestored by reducing, for example, the volume required for the otherfunctions (e.g., liquid pumping, vacuuming) of the robot 10. In someimplementations, the robot 10 carries a volume of cleaning fluid that isat least about 20 percent (e.g. at least about 30 percent, at leastabout 40 percent) of the volume of the robot 10.

Physics and Mobility

The robot 10 is configured to clean approximately 150 square feet ofcleaning surface in a single cleaning operation. A larger or smallertank may permit this to range from 100 square feet to 400 square feet.The duration of the cleaning operation is approximately 45 minutes. Inimplementations with smaller, larger, or 2 or more batteries on board,the cleaning time can range down to 20 minutes or up to 2 hours.Accordingly, the robot 10 is configured (physically, and as programmed)for unattended autonomous cleaning for 45 minutes or more without theneed to recharge a power supply, refill the supply of cleaning fluid orempty the waste materials collected by the robot.

In implementations in which the robot 10 is configured to collectsubstantially all of the cleaning fluid delivered to the surface in asingle pass, the average forward travel speed of the robot 10 can be afunction of the cleaning quality and/or the surface coverage arearequired for a given implementation. For example, slower forward travelspeeds can allow a longer soak time (e.g., longer contact time) betweenthe cleaning fluid and the debris on the surface such that the debriscan be more easily removed from the surface through suction with thesqueegee 208. Additionally or alternatively, faster forward travelspeeds can allow the robot 10 to clean a larger surface area beforerequiring refilling with cleaning liquid and/or recharging the powersupply. Accordingly cleaning quality and surface coverage that isacceptable to consumers is achieved by configuring the robot 10 to allowbetween about 0.3 and about 0.7 seconds of contact between the cleaningliquid and the surface before the cleaning liquid is collected into therobot 10 through squeegee 208. For example, when the robot 10 has adiameter of about 17 centimeters and travels at a forward rate of about25 centimeters/second, the contact time between the cleaning liquid andthe surface is about 0.25 to about 0.6 seconds, the variation in contacttime depending on the positioning of the cleaning fluid distributionrelative to the forward edge of the robot 10 and the positioning of thevacuum assembly relative to the rearward edge of the robot.

In some implementations, the robot 10 includes a navigation systemconfigured to allow the robot 10 to deposit cleaning liquid on a surfaceand subsequently return to collect the cleaning liquid from the surfacethrough multiple passes. As compared to the single-pass configurationdescribed above, such configurations can allow cleaning liquid to beleft on the surface for a longer period of time while the robot 10travels at a higher rate of speed. The navigation system allows therobot 10 to return to positions where the cleaning fluid has beendeposited on the surface but not yet collected. The navigation systemcan maneuver the robot in a pseudo-random pattern across the surfacesuch that the robot is likely to return to the portion of the surfaceupon which cleaning fluid has remained.

As described above, the transverse distance between wheel modules 500,501 (e.g., the wheel base of robot 10) is substantially equal to thetransverse cleaning width (e.g., the transverse width of the wettingelement 204. Thus, during a cleaning operation, wheel modules 500, 501are configured to grip a portion of the surface covered with cleaningliquid. With sufficient traction force, the wheel modules 500, 501 canpropel the robot 10 through the cleaning liquid. With insufficienttraction force, however, the wheel modules 500, 501 can slip on thecleaning liquid and the robot 10 can become stuck in place.

Heavier robots can apply sufficient pressure at wheels to avoid slippingas the wheels pass over the cleaning liquid. As compared to lighterrobots, however, heavier robots are more difficult to handle (e.g., forrefilling at a sink, for carrying to storage). Accordingly, the robot 10is configured to weigh less than 3 kg (fully loaded with cleaningliquid) while wheel modules 500, 501 provide sufficient traction topropel robot 10 through cleaning liquid on distributed on the surface.

In some implementations, the center of gravity of the robot 10 issubstantially along the transverse axis 23 such that much of the weightof the robot 10 is over the wheel modules 500, 501 during a cleaningoperation. Such a weight distribution of robot 10 can exert a sufficientdownward force on wheel modules 500, 501 to overcome slippage while alsoallowing wheel modules 500, 501 to overcome drag forces created aswetting element 204 and squeegee 208 movably contact the surface. Insome implementations, the weight of the robot is distributed to overcomesuch drag forces while applying sufficient cleaning pressure to thesurface (e.g., sufficient pressure to wetting element 204 and squeegee208). For example, the wheel modules 500, 501 can support about 50% toabout 70% of the weight of the robot 10 above the surface. The wettingelement 204 can support at least about 10% of the weight of the robotabove the surface, along the forward portion of the robot. The squeegee208 can support at least about 20% of the weight of the robot above thesurface, along the rearward portion of the robot. As described in detailbelow, the supply volume and the collection volume are configured tomaintain the center of gravity of the robot substantially over thetransverse axis 24 while at least about 25 percent of the total volumeof the robot shifts from cleaning liquid in the supply volume to wastein the collection volume as the cleaning cycle progresses from start tofinish.

In certain implementations, the robot is about 1 kg to about 5 kg full.For household use, the robot can weigh as much as 7 kg full. Exemplaryranges for physical dimensions of the robot are a full mass of 1-10 kg;a cleaning width of 5 cm-40 cm within a diameter of 10-50 cm; a wheeldiameter 1.5 cm-20 cm; drive wheel contact line 2 cm-10 cm for all drivewheels (two, three, four drive wheels); drive wheel contact patch forall wheels 2 cm² or higher.

The robot 10 can be less than about 1.5 kg empty, and less thanapproximately 3 kg full, and carry about 0.5 kg to about 1 kg (or400-1200 ml) of clean or dirty fluid (in the case where the robotapplies fluid as well as picks it up). The waste tank can be sizedaccording to the efficiency of the pick-up process. For example, with acomparatively inefficient squeegee designed to or arranged to leave apredetermined amount of wet fluid on each pass (e.g., so that thecleaning fluid can dwell and progressively work on stains or dried foodpatches), the waste tank can be designed to be equal in size or smallerthan the clean tank. A proportion of the deposited fluid will never bepicked up, and another portion will evaporate before it can be pickedup. In implementations in which an efficient squeegee is used (e.g.,silicone), then it may be necessary to size the waste tank to be equalto or bigger than the clean fluid tank. A proportion of the tank volume,e.g., 5% or higher, may also be devoted to foam accommodation orcontrol, which can increase the size of the waste tank.

To effectively brush, wipe, or scrub the surface, the wetting element204 and the squeegee 208 create drag, and for a robot under 10 kg,should create an average drag of less than about 40% of the weight ofthe robot 10 (e.g., less than about 25% of the weight of the robot).Drag forces (total drag associated with any blades, squeegees, draggingcomponents) should not exceed 25% of robot weight to ensure goodmobility in the absence of active suspensions/constant weight systems,as any lifting obstacle will otherwise remove weight from the tires andaffect motive force. Maximum available traction typically is no morethan about 40% of robot weight on slick surfaces with a surfactant based(low surface tension) cleaning fluid, perhaps as high as 50% in bestcase situations, and traction/thrust must exceed drag/parasitic forces.However, in order to successfully navigate autonomously, to havesufficient thrust to overcome minor hazards and obstacles, to climbthresholds which may encounter the scrubbing or brushing memberdifferently from the wheels, and to escape from jams and other paniccircumstances, the robot 10 can have a thrust/traction, provided mostlyby the driven wheels, of about 150% or more of average drag/parasiticforce. In implementations including a rotating brush, depending on thedirection of rotation, the rotating brush can create drag or thrust.

In some implementations, the robot 10 has a weight of about 1.4 kg fullyloaded, with less than about 100 gram-force of drag (on a surface with astatic coefficient of friction of about 0.38) caused by the wettingelement 204 and less than about 320 gram-force of drag (on a surfacewith a static coefficient of friction of about 0.77) caused by thesqueegee 208, but more than 1100 gram-force of thrust contributed bywheel modules 500, 501 to propel the robot 10 at a maximum forward rateof about 200 mm/s to about 400 mm/s. In certain implementations, weightis added to the robot 10 to improve traction of wheel modules 500, 501by putting more weight on the wheels (e.g., metal handle, clevis-likepivot mount, larger motor than needed, and/or ballast in one embodimentof the present device). With or without added weight, in someimplementations, the robot can include a rotating brush and derive afunctional percentage of thrust from a forwardly rotating brush (whichis turned off generally in reverse), which is not a feature needed in alarge industrial cleaner.

The width of the cleaning head for the mass of a household cleaningrobot, under 10 kg (or even under 20 kg), differs from industrialself-propelled cleaners. This is especially true for wet cleaning. Insome implementations, the robot 10 has at least about 1 cm of (wet)cleaning width for every 1 kg of robot mass (e.g., about 4, 5, or 6 cmof cleaning width for every 1 kg of robot mass), and up to about 20 cmof cleaning width for every kg of robot mass (the higher ratiosgenerally apply to lower masses). For example, the robot 10 can weighapproximately 1.5 kg when fully loaded with cleaning liquid and can havea wet cleaning width of about 16.5 cm, such that the robot 10 can haveabout 11 cm of wet cleaning width for every 1 kg of robot mass.

It can be difficult to apply sufficient wiping or scrubbing force withlarger cleaning width for every kg of robot mass; and lower cleaningwidths per 1 kg of robot mass can lead to either an ineffective cleaningwidth or a very heavy robot unsuitable for consumer use, i.e., thatcannot be carried easily by an ordinary (or frail) person.Self-propelled industrial cleaning machines typically have ⅓ cm ofcleaning width or less per kg machine mass.

Ratios of these dimensions or properties determine whether a robot under5 kg, and in some cases under 10 kg, will be effective for generalhousehold use. Although some such ratios are described explicitly above,such ratios (e.g., cm squared area of wheel contact per kg of robotmass, cm of wheel contact line per kg-force of drag, and the like) areexpressly considered to be inherently disclosed herein, albeit limitedto the set of different robot configurations discussed herein.

In certain implementations, the robot 10 includes tires having a 3 mmfoam tire thickness with 2 mm deep sipes. This configuration performsbest when supporting no more than 3 to 4 kg per tire. The idealcombination of sipes, cell structure and absorbency for a tire isaffected by robot weight. In some implementations, rubber or vinyl tiresare configured with surface features to reduce slippage.

The robot 10 includes at least one wetting element 204 and one squeegee208. For example, a wet vacuum portion can be closely followed by asqueegee to build up the thickness of a deposited water film forpick-up. The squeegee 208 can have sufficient flexibility and range ofmotion to clear any obstacle taller than 2 mm, but ideally to clear theground clearance of the robot (e.g., about a 4½ mm minimum height or theground clearance of the robot).

Any reactionary force exhibited by the squeegee that is directionallyopposite to gravity, i.e., up, subtracts from available traction andshould be less than about 20% of robot weight (e.g., less than about 10%of robot weight). A certain amount of edge pressure, which has an equalreactionary force, is necessary for the squeegee to wipe and collectfluid. In order to obtain an effective combination of fluid collection,reactionary force, wear, and flexible response to obstacles, thephysical parameters of the squeegee are controlled and balanced. Incertain implementations, the squeegee 208 includes a working edge radiusof 3/10 mm for a squeegee less than 300 mm. In some implementations, thesqueegee 208 can have a working edge of about 1/10 to 5/10 mm. Wear,squeegee performance and drag force can be improved with a squeegee ofsubstantially rectangular cross section (optionally trapezoidal) and/or1 mm (optionally about ½ mm to 1½ mm) thickness, 90 degree corners(optionally about 60 to 120 degrees), parallel to the floor within ½ mmover its working length (optionally within up to ¾ mm), and straight towithin 1/500 mm per unit length (optionally within up to 1/100), with aworking edge equal to or less than about 3/10 mm as noted above.Deviations from the above parameters can require greater edge pressure(force opposite to gravity) to compensate, thus decreasing availabletraction.

The wetting element 204 and the squeegee 208 are configured to contactthe floor over a broad range of surface variations (e.g., in wetcleaning scenarios, including tiled, flat, wood, deep grout floors). Insome implementations, the wetting element 204 and/or the squeegee 208are mounted using a floating mount (e.g., on springs, elastomers,guides, or the like) to improve contact with the broad range of surfacevariations. In certain implementations, the wetting element 204 and thesqueegee 208 are mounted to the chassis 100 with sufficient flexibilityfor the designed amount of interference or engagement of the wettingelement 204 and/or the squeegee 208 to the surface. As described above,any reactionary force exhibited by the brushes/scrubbing apparatus thatis opposite to gravity (up) subtracts from available traction and shouldnot exceed 10% of robot weight.

In certain implementations, the robot includes more than one brush,e.g., two counter-rotating brushes with one or more brush on eitherfore-aft side of the center line of the robot, or more. The robot canalso include a differential rotation brush such that two brushes, eachsubstantially half the width of the robot at the diameter of rotation,are placed on either lateral side of the fore-aft axis 22, eachextending along half of the diameter. Each brush can be connected to aseparate drive and motor, and can rotate in opposite directions or inthe same direction or in the same direction, at different speeds ineither direction, which would provide rotational and translationalimpetus for the robot.

The center of gravity of the robot 10 will tend to move during recoveryof fluids unless the cleaner and waste tanks are balanced to continuallymaintain the same center of gravity location. Maintaining the samecenter of gravity location (by tank compartment design) can allow apassive suspension system to deliver the maximum available traction. Therobot 10 includes a tank design that includes a first compartment havinga profile that substantially maintains the position of the compartmentcenter of gravity as it empties, a second compartment having a profilethat substantially maintains the position of the compartment center ofgravity as it fills, wherein the center of gravity of the combined tanksis maintained substantially within the wheel diameter and over thewheels. In some implementations, the robot 10 includes tanks stacked ina substantially vertical direction and configured to maintain the samelocation of the center of gravity of the robot 10.

In certain implementations, absent perfect fluid recovery or activesuspension, superior mobility is achieved either by modeling or assuminga minimum percentage of fluid recovered across all surfaces (70% offluid put down for example) and designing the profile of thecompartments and center of gravity positions according to thisassumption/model. In the alternative, or in addition, setting springforce equal to the maximum unladen (empty tank) condition can contributeto superior traction and mobility. In some implementations, suspensiontravel is at least equal the maximum obstacle allowed by the bumper (andother edge barriers) to travel under the robot.

Maximizing the diameter of the wheels of the robot can decrease theenergy and traction requirements for a given obstacle or depression. Incertain implementations, maximum designed obstacle climbing capabilityshould be 10% of wheel diameter or less. A 4.5 mm obstacle or depressionshould be overcome or tackled by a 45 mm diameter wheel. In certainimplementations, the robot is low for several reasons. The bumper is setlow to distinguish between carpet, thresholds, and hard floors such thata bumper 3 mm from the ground will prevent the robot from mounting mostcarpets (2-5 mm bumper ground clearance, 3 mm being preferable). Theremainder of the robot working surface, e.g., the vacuum assembly, alsohave members extending toward the floor (air guides, squeegees, brushes)that are made more effective by a lower ground clearance. Because theground clearance of one embodiment is between 3-6 mm, the wheels needonly be 30 mm-60 mm. Other wheel sizes can also be used.

Assembly

Referring to FIG. 7, chassis 100 carries a liquid volume 600substantially along an inner portion of the chassis 100. As described indetail below, portions of the liquid volume 600 are in fluidcommunication with liquid delivery and air handling systems carried onthe chassis 100 to allow cleaning fluid to be pumped from the liquidvolume 600 and to allow waste to be suctioned into the liquid volume600. To allow the addition of cleaning liquid and the removal of waste,liquid volume 600 can be accessed through fill door 304 and empty door104 (not shown in FIG. 7).

The wheel modules 500, 501 include respective drive motors 502, 503 andwheels 504, 505. The drive motors 502, 503 releasably connect to thechassis 100 on either side of the liquid volume 600 with the drivemotors 502, 503 positioned substantially over respective wheels 504,505. In some implementations, drive motors 502, 503 are positionedsubstantially horizontal to respective wheels 504, 505 to increase thesize of the liquid volume 600 carried on chassis 100. In someimplementations, wheel modules 500, 501 are releasably connected tochassis 100 and can be removed without the use of tools to facilitate,for example, repair, replacement, and cleaning of the wheel modules 500,501.

A signal channeler 402 is connected to a top portion of chassis 100 andsubstantially covers the liquid volume 600 to allow components to beattached along a substantially top portion of the robot 10. An edge ofthe signal channeler 404 is visible from substantially the entire outercircumference of the robot 10 to allow the signal channeler 404 toreceive a light signal (e.g., an infrared light signal) fromsubstantially any direction. As described in detail below, the signalchanneler 402 receives light from a light source (e.g., a navigationbeacon) and internally reflects the light toward a receiver disposedwithin the signal channeler 402. For example, the signal channeler 402can be at least partially formed of a material (e.g., polycarbonateresin thermoplastic) having an index of refraction of about 1.4 orgreater to allow substantially total internal reflection within thesignal channeler. Additionally or alternatively, the signal channeler402 can include a first mirror disposed along a top surface of thesignal channeler 402 and a second mirror disposed along a bottom surfaceof the signal channeler 402 and facing the first mirror. In thisconfiguration, the first and second mirrors can internally reflect lightwithin the signal channeler 402.

The signal channeler 402 includes a recessed portion 406 that cansupport at least a portion of the user interface 400. A user interfaceprinted circuit board (PCB) can be arranged in the recessed portion 406and covered by a membrane to form a substantially water-tight userinterface 400. As described in detail below, a bottom portion of signalchanneler 402 can form a top portion of the liquid volume 600.

Bumper 300 connects to the hinges 110 arranged substantially along theforward portion of the chassis 100. The hinged connection between bumper300 and chassis 100 can allow the bumper to move a short distancerelative to the chassis 100 when the bumper 300 contacts an obstacle.Bumper 300 is flexibly connected to a fill port 602 of the liquid volume600 such that the bumper 300 and the fill port 602 can flex relative toone another as the bumper 300 moves relative to the chassis 100 uponcontact with an obstacle.

The bumper 300 includes a substantially transparent section 306 near atop portion of the bumper. The transparent section 306 can extendsubstantially along the entire perimeter of the bumper 300. As describedin detail below, the transparent section 306 can be substantiallytransparent to a signal receivable by an omni-directional receiverdisposed substantially near a center portion of the signal channeler 402such that the omni-directional receiver can receive a signal from atransmitter positioned substantially forward of the bumper 300.

The baseplate 200 is carried on a substantially bottom portion ofchassis 100. The baseplate 200 includes pivot hinges that extend from aforward portion of the baseplate 200 and can allow the baseplate 200 tobe snapped into complementary hinge features on the chassis 100. In someimplementations, a user can unhinge the baseplate 200 from the chassis100 without the use of tools. The baseplate 200 carries the trough 202near a forward portion of the robot 10 and a wetting element 204substantially rearward of the trough 202. The baseplate 200 extendsaround a portion of each wheel module 500, 501 to form portion of wheelwells for wheels 504, 505, substantially rearward of the wetting element204. Rearward of the wheels 504, 505, the baseplate 200 carries a vacuumassembly including a squeegee 208 configured in slidable contact withthe surface to pool waste near the contact edge between the squeegee 208and the surface. As described in detail below, the squeegee 208 definesa plurality of orifices substantially near the contact edge between thesqueegee 208 and the surface. As the vacuum assembly 1300 createssuction, waste is lifted from the surface and into the robot through theplurality of orifices defined by the squeegee 208.

In some implementations, a user can unhinge the baseplate 200 from thechassis 100 in order to clean the baseplate 200. In certainimplementations, the user can remove the trough 202, the wetting element204, and/or the squeegee 208 from the baseplate 200 to repair or replacethese components.

Liquid Storage

Referring to FIG. 8, in some implementations, liquid volume 600 canfunction as both a liquid supply volume S and a waste collection volumeW. Liquid volume 600 is configured such that liquid moves from theliquid supply volume S to the surface and then is picked up and returnedto a waste collection volume W. In some implementations, the supplyvolume S and the waste collection volume W are configured to maintain asubstantially constant center of gravity along the transverse axis 24while at least 25 percent of the total volume of the robot 10 shiftsfrom cleaning liquid in the supply volume S to waste in the collectionvolume W as cleaning liquid is dispensed from the applicator and wasteis collected by the vacuum assembly.

In some implementations, all or a portion of the supply volume S is aflexible bladder within the waste collection volume W and surrounded bythe waste collection volume W such that the bladder compresses ascleaning liquid exits the bladder and waste filling the waste collectionvolume W takes place of the cleaning liquid that has exited the bladder.Such a system can be a self-regulating system which can keep the centerof gravity of the robot 10 substantially in place (e.g., over thetransverse axis 24). For example, at the start of a cleaning routine,the bladder can be full such that the bladder is expanded tosubstantially fill the waste collection volume W. As cleaning liquid isdispensed from the robot 10, the volume of the bladder decreases suchthat waste entering the waste collection volume W replaces the displacedcleaning fluid that has exited the flexible bladder. Toward the end ofthe cleaning routine, the flexible bladder is substantially collapsedwithin the waste collection volume W and the waste collection volume issubstantially full of waste.

In some implementations, the maximum volume of the flexible bladder(e.g., the maximum storage volume of cleaning liquid) is substantiallyequal to the volume of the waste collection volume W. In certainimplementations, the volume of the waste collection volume W is larger(e.g., about 10 percent to about 20 percent larger) than the maximumvolume of the flexible bladder. Such a larger waste collection volume Wcan allow the robot 10 to operate in an environment in which the volumeof the waste collected is larger than the volume of the cleaning liquiddispensed (e.g., when the robot 10 maneuvers over substantial spills).

While the supply volume S has been described as a flexible bladdersubstantially surrounded by the waste collection volume W, otherconfigurations are possible. For example, the supply volume S and thewaste collection volume W can be compartments that are stacked orpartially stacked on top of one another with their compartment-fullcenter of gravity within 10 cm of one another. Additionally oralternatively, the supply volume S and the waste collection volume W canbe concentric (concentric such that one is inside the other in thelateral direction); or can be interleaved (e.g., interleaved L shapes orfingers in the lateral direction).

Liquid Applicator

Referring to FIG. 8, a liquid applicator module 1400 applies a volume ofcleaning liquid onto the surface across the width of the wetting element204 which, in some implementations, extends substantially the entirewidth (e.g., diameter) of the robot 10. The liquid applicator module canspray the floor directly, spray a fluid-bearing brush or roller, orapply fluid by dripping or capillary action to the floor, brush, roller,or pad. The liquid applicator module 1400 receives a supply of cleaningliquid from a supply volume S within the liquid volume 600 carried bythe chassis 100. A pump 240 (e.g., a peristaltic pump) pumps thecleaning fluid through the liquid applicator module through one or moreinjection orifices 210 defined by the trough 202 extending along thefront portion of baseplate 200 (see, e.g., FIG. 2). Each injectionorifice 210 is oriented to spray cleaning liquid toward the cleaningsurface. For example, at least a portion of the injection orifices 210can be oriented to spray cleaning liquid toward the cleaning surface, ina direction substantially toward the forward direction of travel of therobot 10. Additionally or alternatively, at least a portion of theinjection orifices 210 can be oriented to spray cleaning liquid towardthe cleaning surface, in a direction substantially toward the rearwarddirection of travel of the robot 10.

The liquid applicator module 1400 includes a supply volume S which, asdescribed in detail below, is a compartment within liquid volume 600.However, in some implementations, supply volume S is a separate volumecarried by the chassis 100. Supply volume S defines an exit aperture 604in fluid communication with a fluid conduit 70. During use, fluidconduit 606 delivers a supply of cleaning liquid to a pump assembly 240(e.g., a peristaltic pump assembly). Pressure created by pump assembly240 forces liquid to trough 202 and through injection orifices 210toward the surface.

The liquid applicator module 1400 applies cleaning liquid to the surfaceat a volumetric rate ranging from about 0.1 mL per square foot to about6.0 mL per square foot (e.g., about 3 mL per square foot). However,depending upon the application, the liquid applicator module 1400 canapply any desired volume of cleaning liquid onto the surface.Additionally or alternatively, the liquid applicator module 1400 can beused to apply other liquids onto the surface such as water,disinfectant, chemical coatings, and the like.

The liquid applicator module 1400 can be a closed system (e.g., whenpump 240 is a peristaltic pump) such that the liquid applicator module1400 can be used to deliver a wide variety of cleaning solutions,including solutions without damaging other components (e.g., seals) ofthe robot 10.

A user can fill the supply container S with a measured volume of cleanwater and a corresponding measured volume of a cleaning agent. The waterand cleaning agent can be poured into the supply volume S through fillport 602 accessible through fill door 304 in bumper 300. The fill port602 can include a funnel to allow for easier pouring of the cleaningliquid into the supply volume S. In some implementations, a filter isdisposed between fill port 602 and the supply volume S to inhibitforeign material from entering the supply volume S and potentiallydamaging the liquid applicator module 1400. The supply volume S has aliquid volume capacity of about 500 mL to about 2000 mL.

Referring to FIGS. 2 and 9, the wetting element 204 can slidably contactthe surface such that the movement of the robot 10 across the surfacecauses the wetting element 204 to spread the cleaning liquid across thesurface. Wetting element 204 is arranged substantially parallel totrough 202 and extends past each end of the trough 202 to allow, forexample, for suitable smearing near the edges of the trough 202. Ends215, 216 of wetting element 204 extend substantially in front ofrespective wheels 504, 505. By smearing cleaning liquid directly infront of wheels 504, 505, wetting element 204 can improve the tractionbetween the wheels 504, 505 and the surface.

Wetting element 204 is a flexible compliant blade including a first edgeconfigured for slidable contact with the surface and a second edgeconfigured for coupling to the chassis 100. The wetting element 204 hasa substantially arcuate shape that extends substantially parallel to theforward perimeter of the robot 10. As the wetting element 204 makesslidable contact with the floor during operation of the robot 10, thesubstantially arcuate can facilitate movement of the robot 10 across thesurface. For example, as compared to a substantially straight wettingelement, the substantially arcuate shape of wetting element 204 cangradually engage a grout line (e.g., of a tiled floor) such the robot 10can adjust to the force required to traverse the grout line.Additionally or alternatively, the substantially arcuate shape of thewetting element 204 can allow for more efficient packaging of componentswithin chassis 100. For example, because at least a portion of thewetting element 204 extends into the chassis, the substantially arcuateshape of the wetting element 204 can allow one or more components (e.g.,a printed circuit board (PCB) to be positioned within the boundarydefined by the wetting element.

Wetting element 204 includes a linear region 218 substantially centeredalong the wetting element 204. The linear region 218 follows acomplementary linear region of baseplate 200 can function as a pivotingleading edge for mounting baseplate 200 on pivot hinges or the like. Insome implementations, wetting element 204 can be mounted and dismountedfrom baseplate 200 separately (e.g., through the use of pivot hingesmounted on the wetting element 204).

Referring to FIG. 10, in some implementations, baseplate 200 includes ascrubbing brush 220 extending substantially along a front portion of thebaseplate 200. The scrubbing brush 220 includes a plurality of bristleclusters 222 extending from the scrubbing brush 220 toward the cleaningsurface. The bristle clusters 222 are spaced (e.g., substantially evenlyspaced) along the scrubbing brush 220. Bristle clusters 222 can eachinclude a plurality of soft compliant bristles with a first end of eachbristle secured in a holder such as a crimped metal channel, or othersuitable holding element. In some implementations, bristle clusters 222are individual plugs press fit into the scrubbing brush 220. A secondend of each bristle is free to bend as each bristle makes contact withthe cleaning surface. These multiple points of contact between thescrubbing brush 220 and the surface can allow the robot 10 to traversesmoothly over perturbations in the surface (e.g., grout lines).

The length and diameter of the bristles of bristle clusters 222, as wellas a nominal interference dimension that the smearing bristles make withrespect to the cleaning surface can be varied to adjust bristlestiffness and to thereby affect the smearing action. In certainimplementations, the scrubbing brush 220 includes nylon bristles withinan average bristle diameter in the range of about 0.05-0.2 mm(0.002-0.008 inches). The nominal length of each bristle isapproximately 16 mm (0.62 inches) between the holder and the cleaningsurface and the bristles are configured with an interference dimensionof approximately 0.75 mm (0.03 inches).

While bristles have been described, other implementations areadditionally or alternatively possible. For example, the scrubbing brush220 can include a woven or nonwoven material, e.g., a scrubbing pad orsheet material configured to contact the surface.

Cleaning liquid can be introduced to the scrubbing brush 220 in any ofvarious different ways. For example, cleaning liquid can be injected ordripped on the surface immediately forward of the scrubbing brush.Additionally or alternatively, cleaning liquid can be introduced throughbristle clusters 222 such that the bristle clusters 222 substantiallywick the cleaning liquid toward the surface.

Additionally or alternatively, the baseplate 200 can carry otherelements configured to spread the cleaning liquid on the surface. Forexample, the baseplate 200 can carry a sponge or a rolling member incontact with the surface.

In some implementations, the baseplate 200 carries one or more activescrubbing elements that are movable with respect to the cleaning surfaceand with respect to the robot chassis. Movement of the active scrubbingelements can increase the work done between the scrubbing element andthe cleaning surface. Each active scrubbing element can be driven formovement with respect to the chassis 100 by a drive module, alsoattached to the chassis 100. Active scrubbing element can also include ascrubbing pad or sheet material held in contact with the cleaningsurface, or a compliant solid element such a sponge or other compliantporous solid foam element held in contact with the surface and vibratedby a vibrated backing element. Additionally or alternatively, activescrubbing elements can include a plurality of scrubbing bristles, and/orany movably supported conventional scrubbing brush, sponge, or scrubbingpad used for scrubbing. In certain implementations, an ultrasoundemitter is used to generate scrubbing action. The relative motionbetween active scrubbing elements and the chassis can include linearand/or rotary motion and the active scrubbing elements can be configuredto be replaceable or cleanable by a user.

Referring to FIG. 11, in some implementations, an active scrubbingelement includes a rotatable brush assembly 604 disposed across thecleaning width, rearward of injection orifices 210, for activelyscrubbing the surface after the cleaning fluid has been applied thereon.The rotatable brush assembly 604 includes a cylindrical bristle holderelement 618 defining a longitudinal axis 629. The bristle holder element618 supports scrubbing bristles 616 extending radially outwardtherefrom. The rotatable brush assembly 604 can be supported on chassis100 for rotation about a rotation axis that extends substantiallyparallel with the cleaning width. The scrubbing bristles 616 are longenough to interfere with the cleaning surface during rotation such thatthe scrubbing bristles 616 are bent by the contact with the cleaningsurface. Additional bristles can be introduced into receiving holes 620.The spacing between adjacent bristle clusters (e.g., bristle clusters622, 624) can be reduced to increase scrubbing intensity.

Scrubbing bristles 616 can be installed in the brush assembly in groupsor clumps with each clump including a plurality of bristles held by asingle attaching device or holder. Clump locations can be disposed alonga longitudinal length of the bristle holder element 618 in one or morepatterns 626, 628. The one or more patterns 626, 628 place at least onebristle clump in contact with cleaning surface across the cleaning widthduring each revolution of the rotatable brush element 604. The rotationof the brush element 604 is clockwise as viewed from the right side suchthat relative motion between the scrubbing bristles 616 and the cleaningsurface tends to move loose contaminants and waste liquid toward therearward direction. Additionally or alternatively, the friction forcegenerated by clockwise rotation of the brush element 604 can drive therobot in the forward direction thereby adding to the forward drivingforce of the robot transport drive system. The nominal dimension of eachscrubbing bristles 616 extended from the cylindrical holder 618 cancause the bristle to interfere with the cleaning surface and there forbend as it makes contact with the surface. The interference dimension isthe length of bristle that is in excess of the length required to makecontact with the cleaning surface. Each of these dimensions along withthe nominal diameter of the scrubbing bristles 616 may be varied toaffect bristle stiffness and therefore the resulting scrubbing action.For example, scrubbing brush element 604 can include nylon bristleshaving a bend dimension of approximately 16-40 mm (0.62-1.6 inches), abristle diameter of approximately 0.15 mm (0.006 inches), and aninterference dimension of approximately 0.75 mm (0.03 inches) to providescrubbing performance suitable for many household scrubbingapplications.

Referring to FIG. 12, in some implementations, an autonomous cleaningrobot 11 includes an extension element 230 carried by the robot 11 alonga substantially forward portion of the robot 11. The extension element230 extends beyond the substantially circular cross-section of the robot11. In use, the extension element 230 contacts the surface and isoriented to push debris back toward the robot such that the debris canbe collected by other components (e.g., wet vacuuming components)carried by the robot 11. The extension element 230 can reach into areas(e.g., corners) that are otherwise substantially inaccessible toautonomous cleaning robots with circular cross-sections. A spring (notshown) can support the extension element 230 on the robot 11 such thatthe spring detents the extension element 230 to an original orientationrelative to the robot 11. In some implementations, the extension element230 includes a flexible compliant blade.

While the extension element has been described as being carried by therobot along a substantially forward portion of the robot, otherimplementations are possible. For example, an extension element can becarried by the robot along a substantially rearward portion of therobot. In such a configuration, the extension element can be in fluidcommunication with the vacuum module (e.g., with the squeegee) such thatdebris is suctioned toward the chassis when the extension elementencounters debris on the surface. The extension element mounted along asubstantially rearward portion of the robot can be spring mounted toallow flexure in response to contact with an obstacle and to return toan original position when it is disengaged from the obstacle.

Air Moving

Referring to FIG. 13, a vacuum module 1300 includes a fan 112 in fluidcommunication with the waste collection volume W and the squeegee 208 incontact with the surface. In use, the fan 112 creates a low pressureregion along the fluid communication path including the waste collectionvolume W and the squeegee 208. As described in further detail below, thefan 112 creates a pressure differential across the squeegee 208,resulting in suction of waste from the surface and through the squeegee208. The suction force created by the fan 112 can further suction thewaste through one or more waste intake conduits 232 (e.g., conduitsdisposed on either end of the squeegee 208) toward a top portion of thewaste collection volume W.

The top portion of the waste collection volume W defines a plenum 608between exit apertures 234 of waste inlet conduits 232 and inletaperture 115 of fan intake conduit 114. While the fan 112 is inoperation, the flow of air and waste through plenum 608 generally movesfrom exit apertures 234 toward the inlet aperture 115. In someimplementations, plenum 608 has a flow area greater than the combinedflow area of the one or more waste intake conduits 232 such that, uponexpanding in the top portion of the waste collection volume W, thevelocity of the moving waste decreases. At this lower velocity, heavierportions of the moving waste (e.g. water and debris) will tend to fallinto the waste collection volume W under the force of gravity whilelighter portions (e.g., air) of the moving waste will continue to movetoward one or more fan inlet conduits 114. The flow of air continuesthrough the fan inlet conduit 114, through the fan 112, and exits therobot 10 through a fan exit aperture 116.

The vacuum module 1300 can include a passive anti-spill system and/or anactive anti-spill system that substantially prevents waste from exitingwaste collection volume W when the robot 10 is not in use (e.g., when auser lifts the robot 10 from the surface). By reducing the likelihoodthat waste will spill from the robot, such anti-spill systems canprotect the user from coming into contact with the waste duringhandling. Additionally or alternatively, such anti-spill systems canreduce the likelihood that waste will contact the fan and potentiallydiminish the performance of the fan over time.

Passive anti-spill systems generally orient flow paths of the vacuummodule 1300 such that spilling is unlikely under normal handlingconditions. In passive anti-spill systems the fan 112 can be positionedat a distance from waste in the waste collection volume W to reduce thelikelihood that waste from the waste collection volume W will reach thefan 112 during handling. For example, in a passive anti-spill system atleast a portion of the fan inlet conduit 114 can be arranged at about 90degrees relative to the direction of flow of the waste liquid into theplenum 608. Accordingly, passive anti-spill systems can include indirect(e.g., winding) flow paths along the vacuum module 1300. To minimizeflow losses resulting from expanding and contracting cross-sections ofthese flow paths, passive anti-spill systems can include flow paths ofsubstantially uniform cross-sectional area. Active anti-spill systemsgenerally include one or more moving parts that move to seal at least aportion of the flow paths of the vacuum module 1300. As compared topassive anti-spill systems, active anti-spill systems can includeshorter and straighter flow paths along the vacuum module 1300 (e.g.,along the plenum 608). Additionally or alternatively, passive anti-spillsystems and active anti-spill systems can include seals throughout thevacuum module 1300 to reduce the likelihood of spilling during normalhandling. Examples of seals that can be used in anti-spill systemsinclude epoxy, ultrasonic welding, plugs, gaskets, and polymericmembranes.

Referring to FIG. 14, the signal channeler 402 can be carried along atop portion of the liquid volume 600 such that a bottom portion of thesignal channeler 402 defines a portion of the plenum 608 in a passiveanti-spill system. As compared to a configuration with a separate signalchanneler and plenum, this configuration can reduce the amount of volumerequired of internal components of the robot 10 and, thus, increase thevolume available for liquid volume 600. In some implementations, thesignal channeler 402 carries at least a portion of the one or more wasteintake conduits 232 and at least a portion of the fan intake conduit114. The fan 112 can be carried on the chassis 100, below liquid volume600 such that the fan 112 is oriented substantially 90 degrees to theflow direction through the plenum 608. Such an orientation can reducethe likelihood of that waste will cross the plenum 608, enter the faninlet conduit 114, and reach the fan 112.

In some implementations of a passive anti-spill system, the one or morewaste intake conduits 232 and the fan intake conduit 114 can be orientedrelative to one another such each exit aperture 234 of the one or morewaste intake conduits 232 is substantially perpendicular to the faninlet aperture 115. Such a perpendicular orientation can reduce thelikelihood that waste will traverse the plenum 608 and reach the fan 112at the end of the fan intake conduit 114.

Referring to FIGS. 15A-B an active anti-spill system 610 can include alinkage 680 extending between a forward seal 682 and one or more rearseals 684. The forward seal 682 is configured to form a substantiallywater right seal over a fan intake conduit 118. The one or more rearseals 684 are configured to form a substantially water tight seal overone or more waste intake conduits 244. A coupler 686 extends between thewheel module 500 and the linkage 680 such that the coupler can transmitat least a portion of the vertical motion of the wheel module 500 to thelinkage 680.

The wheel module 500 is part of a biased-to-drop suspension system suchthat placement of the wheel 500 on the surface 685 forces at least aportion of the wheel module 500 to move upward in a substantiallyvertical direction. As wheel module 500 moves upward in a substantiallyvertical direction, coupler 686 moves along with the wheel module 500 topush linkage 680 to an open position. In the open position, linkage 680holds forward seal 682 and one or more rear seals 684 away from therespective fan intake conduit 118 and one or more waste intake conduits244. With the linkage 680 in the open position, fan intake conduit 118and the one or more waste intake conduits 244 are in fluid communicationsuch that waste can be drawn through the one or more waste intakeconduits 244 toward plenum 608, where waste can fall into the wastecollection volume W (not shown in FIGS. 15A-B) and air can flow towardthe fan intake conduit 118.

When the robot 10 is lifted from the surface, the wheel module 500 movesdownward in a substantially vertical direction. As the wheel module 500moves downward in a substantially vertical direction, coupler 686 movesalong with the wheel module 500 to pull linkage 680 to a closedposition. In the closed position, linkage 680 holds forward seal 682 andone or more rear seals 684 in position to cover (e.g., forming asubstantially water tight seal) the respective fan intake conduit 118and one or more waste linkage conduits 244. With the linkage 680 in theclosed position, fan intake conduit 118 and the one or more waste intakeconduits 244 are not in fluid communication and, thus, waste is lesslikely to enter the fan intake conduit 118 and reach the fan 112.

Coupler 686 has been described as extending between wheel module 500 andlinkage 680. In some implementations, an analogous coupler extendsbetween wheel module 501 and linkage 680 to move the linkage 680 and,thus, move seals 682, 684 between an open and a closed position.

While anti-spill system 610 has been described as including the coupler686, the coupler 686 can be omitted in certain implementations. Forexample, the movement of the wheel module 500 can be detected by aswitch (e.g., a contact switch) in electrical communication with anactuator configured to move the linkage 680 between the open positionand the closed position. Additionally or alternatively, the movement ofthe wheel module 500 can be detected by a hydraulic switch (e.g., usingwaste liquid in the waste collection volume W as the hydraulic fluid).

Referring to FIG. 16, the fan 112 includes a rotary fan motor 704,having a fixed housing 706 and a rotating shaft 708 extending therefrom.The fixed motor housing 706 is disposed in a center portion 709 of a fanscroll 710. A fan seal 711 is configured to engage the fan scroll 710 tosubstantially cover the fan motor 704 disposed substantially within thecenter portion 709 of the fan scroll 710. Together, the fan seal 711 andthe fan scroll 710 form a protective housing that can protect the fanmotor 704 from moisture and debris. The rotating shaft 708 of the fanmotor 704 projects outward through the fan seal 711 to connect to theimpeller 712. In use, the fan motor 704 rotates the rotating shaft 708to turn the impeller 712 and, thus, move air.

The fan impeller 712 includes a plurality of blade elements arrangedabout a central rotation axis thereof and is configured to draw airaxially inward along its rotation axis and expel the air radiallyoutward when the impeller 718 is rotated. Rotation of the impeller 712creates a negative air pressure zone (e.g., a vacuum) on its input sideand a positive air pressure zone at its output side. The fan motor 704is configured to rotate the impeller 712 at a substantially constantrate of rotational velocity, e.g., 14,000 RPM, which generates a higherair flow rate than conventional fans for vacuum cleaners or wet vacuums.Rates as low as about 1,000 RPM and as high as about 25,000 RPM arecontemplated, depending on the configuration of the fan.

Scroll 710 can fold back in on itself to allow a 30 percent largerimpeller, without any loss in scroll volume while maintaining the samepackage size. The inducer is the portion of the fan blade dedicated toinlet flow only. A “moat” (i.e., a channel or wall) can be positioned infront of the impeller to reduce the likelihood of water entering theimpeller. The impeller used for air handling moves air through thesystem at considerable velocity, which can lead to water being pulledout of the dirty tank, through the impeller, and back to the floor. Themoat is configured to prevent or limit this occurrence.

The air flow rate of the fan may range from about 60-100 CFM in free airand about 60 CFM in the robot. In some implementations, the vacuummodule 1300 includes both a wet vacuum subsystem and a dry vacuumsubsystem and the air flow rate of the fan can split (e.g., manuallyadjusted) between the wet and dry vacuum subsystems. Additionally oralternatively, a multi-stage fan design can produce a similar air flowrate, but higher static pressure and velocity, which can help tomaintain flow. Higher velocity also enables the device to entrain dryparticles and lift and pull fluids (e.g., debris mixed with cleaningliquid).

Referring to FIGS. 3 and 13, the exhaust from the fan 112 moves througha pump exit conduit 242 and exits the baseplate 200 through a fanexhaust port 116 substantially rearward of the wetting element andsubstantially forward of the transverse axis 24. Such positioning of thefan exhaust port 116 can, for example, allow the exhaust air flow toagitate the cleaning liquid deposited on the surface prior to collectionby squeegee 208. In some implementations, exhaust from the fan exhaustport 116 is directed substantially toward the wheel modules 500, 501 toimprove traction of the robot 10 over the surface.

Referring again to FIG. 3, the squeegee 208 is configured in slidablecontact with the surface while the robot 10 is in motion. Thepositioning of the squeegee 208 substantially rearward of the wheels504, 505 can stabilize the motion of the robot 10. For example, duringsudden acceleration of the robot 10, the squeegee 208 can prevent therobot from substantially rotating about the transverse axis 24. Byproviding such stabilization, the squeegee 208 can prevent the wettingelement 204 carried on a forward portion of the robot 10 fromsubstantially lifting from the surface. When the overall weight of therobot 10 is less than 3.6 kg, for example, such positioning of thesqueegee 208 can be particularly useful for providing stabilization. Forsuch lightweight robots, the center of gravity of the robot 10 can bepositioned substantially over the transverse axis 24 of the robot suchthat substantial weight is placed over the wheels 504, 505 for tractionwhile the squeegee 208 provides stabilization for the forward directionof travel and the wetting element 204 provides stabilization for thereverse direction of travel.

Referring to FIGS. 3, 17-19, the squeegee 208 includes a base 250extending substantially the entire width of the baseplate 200. Asubstantially horizontal lower section 252 extends downwardly from thebase 250 toward the surface. Edge guides 253, 254 are disposed near eachtransverse end of the base 250 and extend downwardly from the base 250.A plurality of fastener elements 256 extend upwardly from the base 250and are configured to fit (e.g., interference fit) within correspondingapertures on baseplate 200 to hold the squeegee 208 securely in place asthe robot 10 moves about the surface.

The horizontal lower section 252 includes a scraper section 258extending substantially downwardly from an intake section 260. Thescraper section 258 defines a substantially rearward edge of thehorizontal lower section 252. During use, the scraper section 258 formsa slidable contact edge between the squeegee 208 and the surface. Thescraper section 258 is substantially thin and formed of a substantiallycompliant material to allow the scraper section 258 to flex duringslidable contact with the surface. In some implementations, the scrapersection 258 is angled slightly forward to improve collection of wastefrom the surface. In certain implementations, the scraper section 258 isangled slightly rearward to reduce the frictional force required topropel the robot 10 in the forward direction.

The intake section 260 defines a plurality of suction ports 262substantially evenly spaced in the direction of the transverse axis 24to allow, for example, substantially uniform suction in the direction ofthe transverse axis 24 as the robot 10 performs cleaning operations. Thesuction ports 262 each extend through the squeegee 208 (e.g., from alower portion of the horizontal lower section 252 to a top portion ofthe base 250). The suction ports 262 extend through the base such that alower portion of each suction port 262 is substantially near the forwardedge of the scraper section 258. When negative air pressure is generatedby fan 112, waste is suctioned from the forward edge of the scrapersection 258, through the section ports 262, and toward the wastecollection volume W (e.g., as described above).

Edge guides 253, 254 are arranged on respective ends of squeegee 208 andextend downwardly from the base 250 to contact the surface during acleaning operation. The edge guides 253, 254 can be configured to pushwaste toward the fore-aft axis 22 of the robot 10. By guiding wastetoward a center portion of the squeegee 208, the edge guides 253, 254can improve the efficiency of waste collection at the transverse edgesof the robot 10. For example, as compared to robots without edge guides253, 254, the edge guides 253, 254 can reduce streaks left behind by therobot 10.

Edge guides 253, 254 include respective fasteners 263, 264 extendingupward from the edge guides 253, 254 and through the base 250. The edgeguide fasteners 263, 264 extend further from the base than fastenerelements 256 and, in some implementations, fasten into the baseplate 200to reduce the likelihood that the squeegee 250 will become detached fromthe robot 10 during a cleaning operation. In some implementations,fasteners 263, 264 are pressed into the baseplate 200 and held in placethrough an interference fit. In certain implementations fasteners 263,264 are screwed into the chassis 100. Additionally or alternatively, theedge guide fasteners 263 can be fastened to the chassis 100.

Fastener elements 256 extend upwardly from the base 250, along theforward and rearward portions of the base 250. Each fastener element 256is substantially elongate along the transverse axis 24 and includes astem portion 265 and a head portion 266. The squeegee 208 is secured tothe baseplate 200 by pushing fastener elements 256 into correspondingapertures on the baseplate 200. As the fastener elements 256 are pushedinto apertures on the baseplate 200, the head portions 266 deform topass through the apertures. Upon passing through the apertures, eachhead portion 266 expands to its substantially original shape and thehead portion 266 substantially resists passing through the aperture inthe opposite direction. Accordingly, fastener elements 256 substantiallysecure the squeegee 208 to the baseplate.

While the squeegee 208 has been described as being fixed relative to thebaseplate 200, other implementations are possible. In someimplementations, the squeegee can pivot relative to the baseplate 200.For example, the squeegee can pivot about the central vertical axis 20when a lower edge of the squeegee encounters a bump or discontinuity inthe cleaning surface. When the lower edge of the squeegee is free of thebump or discontinuity, the squeegee can return to its normal operatingposition.

In some implementations, the squeegee is a split squeegee. For example,the squeegee can include a forward portion and a rearward portion as twoseparate pieces that can be separately removed from the baseplate forrepair and replacement.

In certain implementations, the squeegee is split into a left portionand a right portion. As the robot spins in place or turns, the squeegeecan assume a configuration in which one side is bent backward and oneside is bent forward. For non-split squeegees, the point at which thebend switches from backward to forward can act as a more or less solidcolumn under the robot, tending to high center it and interfere withmobility. By providing a split in the center of the squeegee, thistendency can be mitigated or eliminated, increasing mobility.

Transport Drive System

Referring again to FIGS. 2-7, the robot 10 is supported for transportover the surface by a transport system 1600. The transport system 1600includes a pair of independent wheel modules 500, 501 respectivelyarranged on the right side and the left side of the chassis. The wettingelement 204 and the squeegee 208 are in slidable contact with thesurface and form part of the transport system 1600. In someimplementations, the transport system 1600 can include a casterpositioned substantially forward and/or substantially rearward of thewheel modules 500, 501. The wheel modules 500, 501 are substantiallyaligned along the transverse axis 24 of the robot 10. The wheel modules500, 501 are independently driven and controlled by the controller 1000to advance the robot 10 in any direction along the surface. The wheelmodules 500, 501 each include a motor and each is coupled to a gearassembly. Outputs of the respective gear assemblies drive the respectivewheel 504, 505.

The controller 1000 measures the voltage and current to each motor andcalculates the derivative of the measured current to each motor. Thecontroller 1000 uses the measured voltage, measured current, and thecalculated derivative of the measured current to determine the speed ofthe motor. For example, the controller 1000 can use a mathematical model(e.g., a DC motor equation) to determine motor speed from the measuredvoltage, measured current, and the calculated derivative. In certainimplementations, the same mathematical model can be used for each drivemotor. The mathematical model can include one or more constants (e.g.,mechanical constants) are calibrated for a given motor. The one or moreconstants can be calibrated using any of various different methods. Forexample, motors can be matched at the factory to have the same constant.As another example, the constants can be calibrated at the factory andstored onboard the robot 10 (e.g. on the controller 1000). As yetanother example, constants can be calibrated for a number of motors ofthe same type and representative values of the constants (e.g.,averages) can be used for each of the motors, provided that thevariation in motor constants is within an acceptable range. As anotherexample, the controller 1000 can include code that learns (e.g., using aneural network) the motor constants over time.

The wheel modules 500, 501 are releasably attached to the chassis 100and forced into engagement with the surface by respective springs. Thewheel modules 500, 501 are substantially sealed from contact with waterusing one or more the following: epoxy, ultrasonic welding, pottingwelds, welded interfaces, plugs, and membranes.

The springs are calibrated to apply substantially uniform force to thewheels along the entire distance of travel of the suspension. The wheelmodules 500, 501 can each move independently in a vertical direction toact as a suspension system. For example, the wheel modules 500, 501 canallow about 4 mm of suspension travel to about 8 mm of suspension travel(e.g., about 5 mm of suspension travel) to allow the robot 10 tonavigate over obstacles on the surface, but to prevent the robot 10 fromcrossing larger thresholds that mark the separation of cleaning areas(e.g., marking the separation between a kitchen floor and a living roomfloor). When the robot 10 is lifted from the surface, the respectivesuspension systems of wheel modules 500, 501 drop the wheel modules 500,501 to the lowest point of travel of the respective suspension system.This configuration is sometimes referred to as a biased-to-dropsuspension system. In some implementations, the wheel modules 500, 501can include a wheel drop sensor that senses when a wheel 504, 505 ofwheel modules 501, 502 moves down and sends a signal to the controller1000. Additionally or alternatively, the controller 1000 can initiatebehaviors that can allow the robot 10 to navigate toward a more stableposition on the surface.

The biased-to-drop suspension system of the robot 10 includes a pivotedwheel assembly including resilience and/or damping, having a ride heightdesigned considering up and down force. In some implementations, thesuspension system delivers within 1-5% (e.g., about 2%) of the minimumdownward force of the robot 10 (i.e., robot mass or weight minus upwardforces from the resilient or compliant contacting members such asbrushes/squeegees, etc). That is, the suspension is resting against“hard stops” with only 2% of the available downward force applied(spring stops having the other 98%, optionally 99%-95%), such thatalmost any obstacle or perturbation capable of generating an upwardforce will result in the suspension lifting or floating the robot overthe obstacle while maintaining maximum available force on the tirecontact patch. This spring force (and in corollary, robot traction) canbe maximized by having an active system that varies its force relativeto the changing robot payload (relative clean and dirty tank level). Insome implementations, actuation for an active suspension is provided byelectrical actuators or solenoids, fluid power, or the like, withappropriate damping and spring resistance. While a pivoted wheelassembly has been described, other implementations are possible. Forexample, the biased-to-drop suspension system can include a verticallytraveling wheel module including conical springs to produce abiased-to-drop suspension system.

Wheels 504, 505 are configured to propel the robot 10 across a wet soapysurface. Referring to FIG. 20, wheel 504 includes a rim 512 configuredto couple to the wheel module 500. The drive wheel module includes adrive motor and a drive train transmission for driving the wheel fortransport. The drive wheel module can also include a sensor fordetecting wheel slip with respect to the surface.

The rim 512 is formed from a stiff material such as a hard moldedplastic to maintain the wheel shape and to provide stiffness. The rim512 provides an outer diameter sized to receive an annular tire 516thereon. The annular tire 516 is configured to provide a non-slip, highfriction drive surface for contacting the surface and for maintainingtraction on the soapy surface.

In one implementation, the annular tire 516 has an internal diameter ofapproximately 37 mm and is sized to fit appropriately over the outerdiameter 514 of rim 512. The annular tire 516 can be bonded, taped orotherwise interference fit to the outer diameter 514 to prevent slippingbetween an inside diameter of the annular tire 516 and the outerdiameter 514 of the rim 512. The tire radial thickness can be about 3mm. The tire material is a chloroprene homopolymer stabilized withthiuram disulfide black with a density of 14-16 pounds per cubic foot,or approximately 15 pounds per cubic foot foamed to a cell size of 0.1mm plus or minus 0.02 mm. The tire has a post-foamed hardness of about69 to 75 Shore 00. The tire material is sold by Monmouth Rubber andPlastics Corporation under the trade name DURAFOAM DK5151HD.

Other tire materials are contemplated, depending on the particularapplication, including, for example, those made of neoprene andchloroprene, and other closed cell rubber sponge materials. Tires madeof polyvinyl chloride (PVC) (e.g., injection molded, extruded) andacrylonitrile-butadiene (ABS) (with or without other extractables,hydrocarbons, carbon black, and ash) may also be used. Additionally,tires of shredded foam construction may provide some squeegee-likefunctionality, as the tires drive over the wet surface being cleaned.Tires made from materials marketed under the trade names RUBATEX R411,R421, R428, R451, and R4261 (manufactured and sold by RubatexInternational, LLC); ENSOLITE (manufactured and sold by Armacell LLC);and products manufactured and sold by American Converters/VAS, Inc.; arealso functional substitutions for the DURAFOAM DK5151 HD identifiedabove.

In certain embodiments, the tire material may contain natural rubber(s)and/or synthetic rubber(s), for example, nitrile rubber (acrylonitrile),styrene-butadiene rubber (SBR), ethylene-propylene rubber (EPDM),silicone rubber, fluorocarbon rubber, latex rubber, silicone rubber,butyl rubber, styrene rubber, polybutadiene rubber, hydrogenated nitrilerubber (HNBR), neoprene (polychloroprene), and mixtures thereof.

In certain embodiments, the tire material may contain one or moreelastomers, for example, polyacrylics (i.e. polyacrylonitrile andpolymethylmethacrylate (PMMA)), polychlorocarbons (i.e. PVC),polyfluorocarbons (i.e. polytetrafluoromethylene), polyolefins (i.e.polyethylene, polypropylene, and polybutylene), polyesters (i.e.polyetheylene terephthalate and polybutylene terephthalate),polycarbonates, polyamides, polyimides, polysulfones, and mixturesand/or copolymers thereof. The elastomers may include homopolymers,copolymers, polymer blends, interpenetrating networks, chemicallymodified polymers, grafted polymers, surface-coated polymers, and/orsurface-treated polymers.

In certain embodiments, the tire material may contain one or morefillers, for example, reinforcing agents such as carbon black andsilica, non-reinforcing fillers, sulfur, cross linking agents, couplingagents, clays, silicates, calcium carbonate, waxes, oils, antioxidants(i.e. para-phenylene diamine antiozonant (PPDA), octylateddiphenylamine, and polymeric 1,2-dihydro-2,2,4-trimethylquinoline), andother additives.

In certain embodiments, the tire material may be formulated to haveadvantageous properties, for example, desired traction, stiffness,modulus, hardness, tensile strength, impact strength, density, tearstrength, rupture energy, cracking resistance, resilience, dynamicproperties, flex life, abrasion resistance, wear resistance, colorretention, and/or chemical resistance (i.e. resistance to substancespresent in the cleaning solution and the surface being cleaned, forexample, dilute acids, dilute alkalis, oils and greases, aliphatichydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, and/oralcohols).

It is noted that cell size of the closed cell foam tires may impactfunctionality, in terms of traction, resistance to contaminants,durability, and other factors. Cell sizes ranging from approximately 20μm to approximately 400 μm may provide acceptable performance, dependingon the weight of the robot and the condition of the surface beingcleaned. Particular ranges include approximately 20 μm to approximately120 μm, with a mean cell size of 60 μm, and more particularlyapproximately 20 μm to approximately 40 μm, for acceptable tractionacross a variety of surface and contaminant conditions.

In certain embodiments, the tires are approximately 13 mm wide, althoughwider tires may provide additional traction. As indicated above, tiresmay be approximately 3 mm thick, although tires of 4 mm-5 mm inthickness or more may be utilized for increased traction. Thinner tiresof approximately 1.5 mm and thicker tires of approximately 4.5 mm may bebeneficial, depending on the weight of the robot, operating speed,movement patterns, and surface textures. Thicker tires may be subject tocompression set. If the cleaning robot is heavier, larger tires may bedesirable nonetheless. Tires with outer rounded or square edges may alsobe employed.

To increase traction, the outside diameter of the tire can be siped.Siping generally provides traction by (a) reducing the transportdistance for fluid removal from the contact patch by providing a voidfor the fluid to move into, (b) allowing more of the tire to conform tothe floor, thereby increasing tread mobility, and (c) providing a wipingmechanism that aids in fluid removal. In at least one instance, the term“siped” refers to slicing the tire material to provide a pattern of thingrooves 1110 in the tire outside diameter. In one embodiment, eachgroove has a depth of approximately 1.5 mm and a width or approximately20 to 300 microns. The siping may leave as little as ½ mm or less oftire base, for example, 3.5 mm deep siping on a 4 mm thick tire. Thegroove pattern can provide grooves that are substantially evenly spacedapart, with approximately 2 to 200 mm spaces between adjacent grooves.“Evenly spaced” may mean, in one instance, spaced apart and with arepeating pattern, not necessarily that every siped cut is the samedistance from the next. The groove cut axis makes an angle G with thetire longitudinal axis. The angle G ranges from about 10-50 degrees, incertain embodiments.

In other embodiments, the siping pattern is a diamond-shaped cross hatchat 3.5 mm intervals, which may be cut at alternating 45 degree angles(.+−.10 degrees) from the rotational axis. Substantially circumferentialsiping, siping that forces away liquid via channels, and other sipingpatterns are also contemplated. Depth and angle of siping may bemodified, depending on particular applications. Moreover, whileincreased depth or width of siping may increase traction, this benefitshould be balanced against impacting the structural integrity of thetire foam. In certain embodiments, for example, it has been determinedthat 3 mm-4 mm thick tires with diamond crossed siping at 7 mm intervalsprovides good tire traction. Larger tires may accommodate a finerpattern, deeper siping, and/or wider siping. Additionally, particularlywide tires or tires made from certain materials may not require anysiping for effective traction. While certain siping patterns may be moreuseful on wet or dry surfaces, or on different types of surfaces, sipingthat provides consistent traction across a variety of applications maybe the most desirable for a general purpose robot cleaner.

While the tires have been described as including a siped outsidediameter, other implementations are possible. For example, the tires canbe Natural Rubber tires with an aggressive diagonal V-rib pattern.

The various tire materials, sizes, configurations, siping, etc., impactthe traction of the robot during use. In certain embodiments, therobot's wheels roll directly through the spray of cleaning solution,which affects the traction, as do the contaminants encountered duringcleaning. A loss of traction of the wheels may cause operatinginefficiencies in the form of wheel slippage, which can lead to therobot deviating from its projected path. This deviation can increasecleaning time and reduce battery life. Accordingly, the robot's wheelsshould be of a configuration that provides good to excellent traction onall surfaces, with the smallest corresponding motor size.

Typical contaminants encountered during cleaning include chemicals,either discharged by the robot or otherwise. Whether in a liquid state(e.g., pine oil, hand soap, ammonium chloride, etc.) or a dry state(e.g., laundry powder, talcum powder, etc.), these chemicals may breakdown the tire material. Additionally, the robot tires may encountermoist or wet food-type contaminants (e.g., soda, milk, honey, mustard,egg, etc.), dry contaminants (e.g., crumbs, rice, flour, sugar, etc.),and oils (e.g., corn oil, butter, mayonnaise, etc.). All of thesecontaminants may be encountered as residues, pools or slicks, or driedpatches. The tire materials described above have proven effective inresisting the material breakdown caused by these various chemicals andoils. Additionally, the cell size and tire siping described has provenbeneficial in maintaining traction while encountering both wet and drycontaminants, chemical or otherwise. Dry contaminants at certainconcentrations, however, may become lodged within the siping. Thechemical cleaner used in the device, described below, also helpsemulsify certain of the contaminants, which may reduce the possibledamage caused by other chemical contaminants by diluting thosechemicals.

In addition to contaminants that may be encountered during use, thevarious cleaning accessories (e.g., brushes, squeegees, etc.) of thedevice affect the traction of the device. The drag created by thesedevices, the character of contact (i.e., round, sharp, smooth, flexible,rough, etc.) of the devices, as well as the possibility of slippagecaused by contaminants, varies depending on the surface being cleaned.Limiting the areas of contact between the robot and the surface beingcleaned reduces attendant friction, which improves tracking and motion.One and one-half pounds of drag force versus three to five pounds ofthrust has proven effective in robots weighing approximately 5-15pounds. Depending on the weight of the robot cleaner, these numbers mayvary, but it is noted that acceptable performance occurs at less thanabout 50% drag, and is improved with less than about 30% drag.

The tire materials (and corresponding cell size, density, hardness,etc.), siping, robot weight, contaminants encountered, degree of robotautonomy, floor material, and so forth, all impact the total tractioncoefficients of the robot tires. For certain robot cleaners, thecoefficient of traction (COT) for the minimum mobility threshold hasbeen established by dividing a 0.9 kg-force drag (as measured duringsqueegee testing) by 2.7 kg-force of normal force, as applied to thetires. Thus, this minimum mobility threshold is approximately 0.33. Atarget threshold of 0.50 was determined by measuring the performance ofshredded black foam tires. Traction coefficients of many of thematerials described above fell within a COT range of 0.25 to 0.47, thuswithin the acceptable range between the mobility threshold and thetarget threshold. Additionally, tires that exhibit little variability intraction coefficients between wet and dry surfaces are desirable, giventhe variety of working conditions to which a cleaning robot is exposed.

The robot cleaning device may also benefit by utilizing sheaths orbooties that at least partially or fully surround the tires. Absorbentmaterials, such as cotton, linen, paper, silk, porous leather, chamois,etc., may be used in conjunction with the tires to increase traction.Alternatively, these sheaths may replace rubberized wheels entirely, bysimply mounting them to the outer diameter 1104 of the cup shaped wheelelement 1102. Whether used as sheaths for rubber tires or as completereplacements for the rubber tires, the materials may be interchangeableby the user or may be removed and replaced via automation at a base orcharging station. Additionally, the robot may be provided to the enduser with sets of tires of different material, with instructions to useparticular tires on particular floor surfaces.

The cleaning solution utilized in the robot cleaner should be able toreadily emulsify contaminants and debond dried waste from surfaces,without damaging the robot or surface itself. Given the adverse effectsdescribed above with regard to robot tires and certain chemicals, theaggressiveness of the cleaning solution should be balanced against theshort and long-term negative impacts on the tires and other robotcomponents. In view of these issues, virtually any cleaning materialthat meets the particular cleaning requirements may be utilized with thecleaning robot. In general, for example, a solution that includes both asurfactant and a chelating agent may be utilized. Additionally, a pHbalancing agent such as citric acid may be added. Adding a scent agent,such as eucalyptus, lavender, and/or lime, for example, may improve themarketability of such a cleaner, contributing to the perception on thepart of the consumer that the device is cleaning effectively. A blue,green, or other noticeable color may also help distinguish the cleanerfor safety or other reasons. The solution may also be diluted and stilleffectively clean when used in conjunction with the robot cleaner.During operation, there is a high likelihood that the robot cleaner maypass over a particular floor area several times, thus reducing the needto use a full strength cleaner. Also, diluted cleaner reduces the wearissues on the tires and other components, as described above. One suchcleaner that has proven effective in cleaning, without causing damage tothe robot components, includes alkyl polyglucoside (for example, at 1-3%concentration) and tetrapotassium ethylenediamine-tetraacetate(tetrapotassium EDTA) (for example, at 0.5-1.5% concentration). Duringuse, this cleaning solution is diluted with water to produce a cleaningsolution having, for example, approximately 3-6% cleaner andapproximately 94-97% water. Accordingly, in this case, the cleaningsolution actually applied to the floor may be as little as 0.03% to0.18% surfactant and 0.01 to 0.1% chelating agent. Of course, othercleaners and concentrations thereof may be used with the disclosed robotcleaner.

For example, the families of surfactants and chelating agents disclosedin U.S. Pat. No. 6,774,098, the disclosure of which is herebyincorporated by reference in its entirety, are also suitable forapplication in the robot having the tire materials and configurationsdisclosed. To balance the aggressiveness of the cleaners disclosed inthe '098 patent with the wear caused on the machine components, however,it is preferred that the cleaning agents should (i) include no solvent,or include solvent at a percentage lower than that of the chelatingagent of an alcohol solvent, or have the disclosed solvents in ½ to1/100 the concentrations, and/or (ii) be further diluted fordeterministic single pass, deterministic repeat passes, or randommultipass use in a robot by 20%+/−15% (single pass), 10%+/−8% (repeatpass), and from 5% to 0.1% (random multipass) respectively, of theconcentrations disclosed; and/or (iii) be further combined with ananti-foaming agent known to be compatible with the selected surfactantand chelating agent in percentages the same as or lower than commercialcarpet cleaners, e.g., less than 5% of silicone emulsion, and/or (iv)replaced with or compatibly mixed with an odor remover of viablebacterial cultures.

In certain embodiments, the cleaning solution utilized in the robotcleaner includes (or is) one or more embodiments of the “hard surfacecleaner” described in U.S. Pat. No. 6,774,098, preferably subject to(i), (ii), (iii), and/or (iv) above. Certain embodiments of the “hardsurface cleaner” in U.S. Pat. No. 6,774,098, are described in thefollowing paragraphs.

In one embodiment, the hard surface cleaner comprises: (a) a surfactantsystem consisting of amine oxides within the general formula (I): orquaternary amine salts within the general formula (II): or combinationsof the foregoing amine oxides and quaternary amine salts; and (b) a veryslightly water-soluble polar organic compound having a water solubilityranging from about 0.1 to 1.0 weight percent, a weight ratio of the veryslightly water-soluble polar organic compound to the surfactant systemranging from about 0.1:1 to about 1:1, wherein R¹ and R² are the same ordifferent and are selected from the group consisting of methyl, ethyl,propyl, isopropyl, hydroxyethyl and hydroxypropyl, R³ is selected fromthe group consisting of straight chain alkyls, branched chain alkyls,straight chain heretroalkyls, branched chain heteroalkyls and alkylethers, each having from about 10 to 20 carbon atoms, R⁴ is selectedfrom the group consisting of alkyl groups having from 1 to about 5carbon atoms, and X is a halogen atom.

In another embodiment, the hard surface cleaner comprises: (a) either(i) a combination of a nonionic surfactant and a quaternary ammoniumsurfactant or (ii) an amphoteric surfactant, the total amount of thesurfactant being present from about 0.001-10%, wherein the nonionicsurfactant is selected from the group consisting of an alkoxylatedalkylphenol ether, an alkoxylated alcohol, or a semi-polar nonionicsurfactant which itself is selected from the group consisting ofmono-long-chain alkyl, di-short-chain trialkyl amine oxides,alkylamidodialkyl amine oxides, phosphine oxides and sulfoxides; (b) nomore than 50% of at least one water-soluble or dispersible organicsolvent having a vapor pressure of at least 0.001 mm Hg at 25.degree.C.; (c) 0.01-25% of tetraammonium ethylenediamine-tetraacetate(tetraammonium EDTA) as a chelating agent; and (d) water.

In yet another embodiment, the hard surface cleaner comprises (a) asurfactant selected from the group consisting of anionic, nonionicsurfactants, and mixtures thereof, with optionally, a quaternaryammonium surfactant, the total amount of surfactant being present fromabout 0.001-10% by weight; (b) at least one water-soluble or dispersibleorganic solvent having a vapor pressure of at least 0.001 mm Hg at25.degree. C., the at least one organic solvent being selected from thegroup consisting of alkanols, diols, glycol ethers, and mixtures thereofpresent in an amount from about 1% to 50% by weight of the cleaner; (c)tetrapotassium ethylenediamine-tetraacetate (potassium EDTA) as achelating agent, the potassium EDTA present from about 0.01-25%weight—of the cleaner; and (d) water.

In still another embodiment, the hard surface cleaner comprises (a) anonionic surfactant with optionally, a quaternary ammonium surfactant,the total amount of the surfactant being present from about 0.001-10%,wherein the nonionic surfactant is selected from the group consisting ofan alkoxylated alkylphenol ether, an alkoxylated alcohol, or asemi-polar nonionic surfactant which itself is selected from the groupconsisting of mono-long-chain alkyl, di-short-chain trialkyl amineoxides, alkylamidodialkyl amine oxides, phosphine oxides and sulfoxides;(b) no more than 50% of at least one water-soluble or dispersibleorganic solvent having a vapor pressure of at least 0.001 mm Hg at25.degree. C.; (c) 0.01-25% of tetraammoniumethylenediamine-tetraacetate (tetraammonium EDTA) as a chelating agent;and (d) water.

In certain embodiments, the hard surface cleaner has a viscosity of lessthan about 100 cps and comprises: (a) at least about 85% water, in whichis dissolved (b) at least about 0.45 equivalent per kilogram of aninorganic anion which, when combined with calcium ion, forms a saltwhich has a solubility of not more than 0.2 g/100 g water at 25.degree.C., wherein the anion is carbonate, fluoride, or metasilicate ion, or amixture of such anions, (c) at least 0.3% by weight, based on the weightof the composition, of a detersive surfactant including an amine oxideof the form RR¹R²N→O wherein R is C₆-C₁₂ alkyl and R¹ and R² areindependently C₁₋₄ alkyl or C₁₋₄ hydroxyalkyl, and (d) at least about0.5 weight percent of a bleach, based upon the weight of thecomposition, wherein the cleaning composition is alkaline andessentially free of chelating agents, phosphorus-containing salt, andabrasive.

In certain embodiments, the cleaning solution utilized in the robotcleaner includes (or is) one or more embodiments of the hard surfacecleaners described in U.S. Pat. Nos. 5,573,710, 5,814,591, 5,972,876,6,004,916, 6,200,941, and 6,214,784, all of which are incorporatedherein by reference.

U.S. Pat. No. 5,573,710 discloses an aqueous multiple-surface cleaningcomposition which can be used for the removal of grease and stains fromhard surfaces or hard fibrous substrates such as carpet and upholstery.The composition contains (a) a surfactant system consisting of amineoxides within the general formula (I): or quaternary amine salts withinthe general formula (II): or combinations of the foregoing amine oxidesand quaternary amine salts; and (b) a very slightly water-soluble polarorganic compound. The very slightly water-soluble polar organic compoundmay have a water solubility ranging from about 0.1 to 1.0 weightpercent, and the weight ratio of the very slightly water-soluble polarorganic compound to the surfactant system may range from about 0.1:1 toabout 1:1. R¹ and R² may be selected from the group consisting ofmethyl, ethyl, propyl, isopropyl, hydroxyethyl and hydroxypropyl. R¹ andR² may be the same or different. R³ may be selected from the groupconsisting of straight chain alkyls, branched chain alkyls, straightchain heretroalkyls, branched chain heteroalkyls and alkyl ethers, eachhaving from about 10 to 20 carbon atoms. R⁴ may be selected from thegroup consisting of alkyl groups having from 1 to about 5 carbon atoms.X is a halogen atom.

In certain cases, the composition further includes a water solubleorganic compound in an amount effective to reduce streaking. The watersoluble organic compound may be selected from water soluble glycolethers and water soluble alkyl alcohols. The water soluble organiccompound may have a water solubility of at least 14.5 weight percent.The weight ratio of the surfactant system to the water soluble organiccompound may range from about 0.033:1 to about 0.2:1.

U.S. Pat. No. 5,814,591 describes an aqueous hard surface cleaner withimproved soil removal. The cleaner includes (a) either (i) a nonionic,an amphoteric surfactant, or a combination thereof, or (ii) a quaternaryammonium surfactant, the surfactants being present in a cleaningeffective amount; (b) at least one water-soluble or dispersible organicsolvent having a vapor pressure of at least 0.001 mm Hg at 25.degree.C., the at least one organic solvent present in a solubilizing- ordispersion-effective amount; (c) ammonium ethylenediamine-tetraacetate(ammonium EDTA) as a chelating agent, the ammonium EDTA present in anamount effective to enhance soil removal in the cleaner; and (d) water.The total surfactant may be present in an amount from about 0.001-10%.In a concentrated product, the surfactant may be present up to 20% byweight. The nonionic surfactant may be selected from the groupconsisting of an alkoxylated alkylphenol ether, an alkoxylated alcohol,or a semi-polar nonionic surfactant which itself is selected from thegroup consisting of mono-long-chain alkyl, di-short-chain trialkyl amineoxides, alkylamidodialkyl amine oxides, phosphine oxides and sulfoxides.The at least one water-soluble or dispersible organic solvent may bepresent in an amount of no more than 50% by weight of the cleaner. Theammonium EDTA may be a tetraammonium EDTA and present in an amount ofabout 0.01-25% by weight of the total cleaner.

U.S. Pat. No. 5,972,876 discloses an aqueous hard surface cleanercomprising (a) a surfactant selected from the group consisting ofanionic, nonionic surfactants, and mixtures thereof, with optionally, aquaternary ammonium surfactant, the total amount of surfactant beingpresent in a cleaning-effective amount; (b) at least one water-solubleor dispersible organic solvent having a vapor pressure of at least 0.001mm Hg at 25.degree. C., the organic solvent being present in asolubilizing- or dispersion-effective amount; (c) tetrapotassiumethylenediamine-tetraacetate (potassium EDTA) as a chelating agent, thepotassium EDTA present in an amount effective to enhance soil removal inthe cleaner; and (d) water. The total amount of surfactant may bepresent from about 0.001-10% by weight. The at least one organic solventmay be selected from the group consisting of alkanols, diols, glycolethers, and mixtures thereof, and is present in an amount from about 1%to 50% by weight of the cleaner. The potassium EDTA may be present fromabout 0.01-25% weight of the cleaner.

U.S. Pat. No. 6,004,916 discloses an aqueous, hard surface cleaner whichcontains (a) either a nonionic or amphoteric surfactant with optionally,a quaternary ammonium surfactant, the surfactants being present in acleaning effective amount; (b) at least one water-soluble or dispersibleorganic solvent having a vapor pressure of at least 0.001 mm Hg at25.degree. C., the at least one organic solvent present in asolubilizing- or dispersion-effective amount; (c) ammoniumethylenediamine-tetraacetate (ammonium EDTA) as a chelating agent, theammonium EDTA present in an amount effective to enhance soil removal inthe cleaner; and (d) water. The surfactant may be a nonionic surfactantwith optionally, a quaternary ammonium surfactant. The nonionicsurfactant may be selected from the group consisting of an alkoxylatedalkylphenol ether, an alkoxylated alcohol, or a semi-polar nonionicsurfactant which itself is selected from the group consisting ofmono-long-chain alkyl, di-short-chain trialkyl amine oxides,alkylamidodialkyl amine oxides, phosphine oxides and sulfoxides. Thetotal amount of the surfactant may be present from about 0.001-10%. Theat least one water-soluble or dispersible organic solvent may be presentin an amount of no more than 50% by weight of the cleaner. The ammoniumEDTA may be a tetraammonium EDTA which is present in an amount from0.01-25% by weight of the total cleaner.

U.S. Pat. No. 6,200,941 discloses a diluted hard surface cleaningcomposition. The cleaning composition contains (a) at least about 85%water, in which is dissolved (b) at least about 0.45 equivalent perkilogram of an inorganic anion which, when combined with calcium ion,forms a salt which has a solubility of not more than 0.2 g/100 g waterat 25.degree. C.; (c) at least 0.3% by weight, based on the weight ofthe composition, of a detersive surfactant. The composition preferablyhas a viscosity of less than about 100 cps. The anion may be carbonate,fluoride, or metasilicate ion, or a mixture of such anions. Thedetersive surfactant may include an amine oxide of the form RR¹R²N→Owherein R is C₆-C₁₂ alkyl and R¹ and R² are independently C₁₄ alkyl orC₁₄ hydroxyalkyl. The composition may further contain at least about 0.5weight percent of a bleach, based upon the weight of the composition. Inone case, the cleaning composition is alkaline and essentially free ofchelating agents, phosphorus-containing salt, and abrasive.

U.S. Pat. No. 6,214,784 describes a composition similar to thatdisclosed in U.S. Pat. No. 5,972,876. The composition may includedipotassium carbonate as a buffer.

Controller Module

Control module 1000 is interconnected for two-way communication witheach of a plurality of other robot subsystems. The interconnection ofthe robot subsystems is provided via network of interconnected wires andor conductive elements, e.g. conductive paths formed on an integratedprinted circuit board or the like, as is well known. In someimplementations, the two-way communication between the control module1000 one or more of the robot subsystems occurs through a wirelesscommunication path. The control module 1000 at least includes aprogrammable or preprogrammed digital data processor, e.g. amicroprocessor, for performing program steps, algorithms and ormathematical and logical operations as may be required. The controlmodule 1000 also includes a digital data memory in communication withthe data processor for storing program steps and other digital datatherein. The control module 1000 also includes one or more clockelements for generating timing signals as may be required.

In general, the robot 10 is configured to clean uncarpeted indoor hardfloor surface, e.g. floors covered with tiles, wood, vinyl, linoleum,smooth stone or concrete and other manufactured floor covering layersthat are not overly abrasive and that do not readily absorb liquid.Other implementations, however, can be adapted to clean, process, treat,or otherwise traverse abrasive, liquid-absorbing, and other surfaces.Additionally or alternatively, the robot 10 can be configured toautonomously transport over the floors of small enclosed furnished roomssuch as are typical of residential homes and smaller commercialestablishments. The robot 10 is not required to operate over predefinedcleaning paths but may move over substantially all of the cleaningsurface area under the control of various transport algorithms designedto operate irrespective of the enclosure shape or obstacle distribution.For example, the robot 10 can move over cleaning paths in accordancewith preprogrammed procedures implemented in hardware, software,firmware, or combinations thereof to implement a variety of modes, suchas three basic operational modes, i.e., movement patterns, that can becategorized as: (1) a “spot-coverage” mode; (2) a “wall/obstaclefollowing” mode; and (3) a “bounce” mode. In addition, the robot 10 ispreprogrammed to initiate actions based upon signals received fromsensors incorporated therein, where such actions include, but are notlimited to, implementing one of the movement patterns above, anemergency stop of the robot 10, or issuing an audible alert. Theseoperational modes of the robot are specifically described in U.S. Pat.No. 6,809,490, by Jones et al., entitled, Method and System forMulti-Mode Coverage for an Autonomous Robot, the entire disclosure ofwhich is herein incorporated by reference it its entirety. However, thepresent disclosure also describes alternative operational modes.

The robot 10 also includes the user interface 400. The user interface400 provides one or more user input interfaces that generate anelectrical signal in response to a user input and communicate the signalto the controller 1000. A user can input user commands to initiateactions such as power on/off, start, stop or to change a cleaning mode,set a cleaning duration, program cleaning parameters such as start timeand duration, and or many other user initiated commands. While the userinterface 400 has been described as a user interface carried on therobot 10, other implementations are additionally or alternativelypossible. For example, a user interface can include a remote controldevice (e.g., a hand held device) configured to transmit instructions tothe robot 10. Additionally or alternatively, a user interface caninclude a programmable computer or other programmable device configuredto transmit instructions to the robot 10. In some implementations, therobot can include a voice recognition module and can respond to voicecommands provided by the user. User input commands, functions, andcomponents contemplated for use with the present invention arespecifically described in U.S. patent application Ser. No. 11/166,891,by Dubrovsky et al., filed on Jun. 24, 2005, entitled Remote ControlScheduler and Method for Autonomous Robotic Device, the entiredisclosure of which is herein incorporated by reference it its entirety.Specific modes of user interaction are also described herein.

Sensor Module

The robot 10 includes a sensor module 1100. The sensor module 1100includes a plurality of sensors attached to the chassis and integratedwith the robot subsystems for sensing external conditions and forsensing internal conditions. In response to sensing various conditions,the sensor module 1100 can generate electrical signals and communicatethe electrical signals to the controller 1100. Individual sensors canperform any of various different functions including, but not limitedto, detecting walls and other obstacles, detecting drop offs in thesurface (sometimes referred to as cliffs), detecting debris on thesurface, detecting low battery power, detecting an empty cleaning fluidcontainer, detecting a full waste container, measuring or detectingdrive wheel velocity distance traveled or slippage, detecting cliff dropoff, detecting cleaning system problems such rotating brush stalls orvacuum system clogs or pump malfunctions, detecting inefficientcleaning, cleaning surface type, system status, temperature, and manyother conditions. In particular, several aspects of the sensor module1100 as well as its operation, especially as it relates to sensingexternal elements and conditions are specifically described in U.S. Pat.No. 6,594,844, by Jones, entitled Robot Obstacle Detection System, andU.S. patent application Ser. No. 11/166,986, by Casey et al., filed onJun. 24, 2005, entitled Obstacle Following Sensor Scheme for a MobileRobot, the entire disclosures of which are herein incorporated byreference it their entireties.

The robot 10 includes control and sensor components in close proximityto the wet cleaning components. As described above, the robot 10 can besized to fit within any of various different confined spaces typicallyencountered in household cleaning applications. Accordingly, much of thevolume of robot 10 is occupied by the liquid storage 1500, liquidapplicator 1400, and vacuum subsystems 1300, each of which can includethe transport of water, solvents, and/or waste throughout the robot 10.As distinguished from many dry vacuuming robots that do not use wetcleaners and do not generate waste, some of the sensors and controlelements of the robot 10 are sealed and/or positioned to minimizeexposure to water or more damaging cleaning fluids or solvents. Asdistinguished from many industrial cleaners, some of the sensors andcontrol elements of the robot 10 are packaged in close proximity to(e.g., within less than about an inch of) cleaning elements, cleaningfluids, and/or waste.

The controller 1000 can be implemented using a PCB carried by thechassis 100 and secured in any of various different positions along thechassis. For example, the PCB can be carried on a top portion of thesignal channeler 402, in the recessed portion 406.

The entire main control PCB is fluid sealed, either in a water resistantor waterproof housing having at least JIS grade 3 (mild spray)water/fluid resistance, but grade 5 (strong spray), grade 7 (temporaryimmersion), and ANSI/IEC 60529-2004 standards for equivalent wateringress protection are also desirable. In some implementations, the maincontrol PCB is sealed in a JIS grade 3-7 housing (1) by a screwed-downand gasketed cover over the main housing; (2) by a welded, caulked,sealed, or glued cover secured to the main housing; (3) by beingpre-assembled in a water resistant, water-tight, water-proof, orhermetically sealed compartment or module; or (4) by being positioned ina volume suitable for potting or pre-potted in resin or the like.

Many sensor elements have a local small circuit board, sometimes with alocal microprocessor and/or A/D converter and the like, and thesecomponents are often sensitive to fluids and corrosion. In someimplementations, sensor circuit boards distributed throughout the bodyof the robot 10 are sealed in a JIS grade 3-7 housing in a similarmanner. In some implementations, multiple circuit boards, including atleast the main circuit board and one remote circuit board (e.g., a userinterface circuit board) several centimeters from the main board, may besealed by a single matching housing or cover. For example, all or someof the circuit boards can be arranged in a single plastic or resinmodule having extensions which reach to local sensor sites. Additionallyor alternatively, a distributed cover can be secured over all of thecircuit boards. Exposed electrical connections and terminals of sensors,motors, or communication lines can be sealed in a similar manner, withcovers, modules, potting, shrink fit, gaskets, or the like. In thismanner, substantially the entire electrical system is fluid-sealedand/or isolated from cleaning liquid and/or waste. Any and allelectrical or electronic elements defined herein as a circuit board,PCB, detector, sensor, etc., are candidates for such sealing.

Referring to FIG. 21, electrical components (e.g., a PCB, the fan 112)of the robot 10 can be substantially isolated from moisture and/or wasteusing a wire seal 120. The wire seal 120 defines one or more apertures122 extending through the wire seal 120 such that lead wires of anelectrical component can be passed from one side of the wire seal 120 tothe other, through the one or more apertures 122. With lead wiresextending through the one or more apertures 122, a sealant (e.g.,potting material) can be introduced into the one or more apertures 122to hold the lead wires in place. In use, the wire seal 120 can bepositioned on the robot 10 such that the electrical component is mountedin a substantially dry portion of the robot 10 while the lead wiresextend through the wire seal 120 toward a wet portion of the robot 10.The sealing provided by the wire seal 120 can protect the electricalcomponent from damage due to moisture and/or waste.

Omni-Directional Receiver

Referring to FIG. 22, the robot 10 includes an omni-directional receiver410 disposed along a bottom portion of signal channeler 402. For thepurpose of illustration, FIG. 22 shows the signal channeler 402 withoutwaste intake conduits 234 and without fan intake conduit 114 attached.Several aspects of the omni-directional sensor 410 as well as itsoperation, especially as it relates to the navigation and direction ofthe robot 10 are specifically described in U.S. patent application Ser.No. 11/633,869, by Ozick et al., entitled “AUTONOMOUS COVERAGE ROBOTNAVIGATION SYSTEM,” the entire disclosure of which is hereinincorporated by reference in its entirety.

The omni-directional receiver 410 is positioned on the signal channeler402, substantially off-center from (e.g., substantially forward of) thecentral vertical axis 20 of the robot 10. The off-center positioning ofomni-directional receiver 410 can allow the control module 1000 to bemore sensitive in one direction. In some implementations, suchsensitivity allows the robot 10 to discern directionality duringmaneuvers. For example, if the omni-directional receiver 410 receives asignal, the control module 1000 can direct the robot 10 to turn in placeuntil the signal received by the omni-directional receiver 410 weakensand/or disappears. In some implementations, the control module 1000directs the robot 10 to drive in the direction in which a weakenedsignal and/or no signal is detected (e.g., away from the source of thesignal) and, if the robot 10 turns 360 degrees and is still stuck in thebeam, the robot 10 will turn 180 degrees and drive forward in a lastattempt to get free.

As shown in FIG. 22, the omni-directional receiver 410 can be disposedsubstantially along a bottom portion 403 of the signal channeler 402,facing toward the chassis 100. As compared to a configuration in whichan omni-directional receiver extends from a top surface of the signalchanneler (e.g., forming the highest point of the robot), disposing theomni-directional receiver 410 along the bottom portion 403 of the signalchanneler 402 can lower the overall height profile of the robot 10.Additionally or alternatively, this configuration can protect theomni-directional receiver 410 from damage as the robot 10 maneuversthrough tight spaces and/or bumps into an overhead obstruction.

In some implementations, the omni-directional receiver 410 can beconfigured to receive transmissions of infrared light (IR). In suchimplementations, a guide (e.g. a light pipe) can guide emissionsreflected off a conical reflector and channel them to an emissionreceiver.

The omni-directional receiver 410 is disposed substantially within acavity 414 defined by a housing 412. A cover 416 extends over the cavity414 and forms a substantially water-tight seal with the housing 412 toenclose the omni-directional receiver 410. In some implementations, thecover 416 is releasably attached to the housing 412 to allow, forexample, replacement and/or repair of the omni-directional receiver 410.The substantially water-tight seal between the housing 412 and the cover414 can include any of various different seals. Examples of sealsinclude epoxy, ultrasonic welding, potting wells, welded interfaces,plugs, gaskets, and polymeric membranes.

During use, an active external device (e.g., a navigation beacon) cansend a signal toward the signal channeler 402. The signal channeler 402is configured for total internal reflection of the incident signal suchthat the signal moves substantially unattenuated within the signalchanneler 402 (e.g., within the material forming the signal channeler).In some implementations, the signal channeler 402 is a substantiallyuniform layer of polished polycarbonate resin thermoplastic. The signalmoving through the signal channeler 402 is internally reflected throughthe signal channeler 402. The omni-directional receiver 410 is arrangedto detect signal reflected through the signal channeler. Theomni-directional receiver 416 is in communication (e.g., electricalcommunication) with the control module 1000. Upon detecting a signaltraveling through the signal channeler 402, the omni-directionalreceiver 416 sends a signal to the control module 1000.

In some implementations, the control module 1000 responds to the signalfrom the omni-directional receiver 416 by controlling the wheel modules500, 501 to navigate the robot 10 away from the source of the signal.For example, as an initial escape procedure, the control module 1000 candirect the wheel modules 500, 501 to move the robot 10 in a rearwarddirection. Such movement in the rearward direction, can position therobot 10 further away from the beam such that robot 10 can determinedirectionality (e.g., spin out of the beam) by rotating substantially inplace. In a subsequent escape procedure, the controller 1000 can directthe robot 10 in a direction away from the signal.

In some implementations, the robot 10 is configured to detect thevirtual wall pattern and is programmed to treat the virtual wall patternas a room wall so that the robot does not pass through the virtual wallpattern.

In some implementations, the robot 10 includes a radio to control thestate of the navigation beams through commands transmitted over a packetradio network.

Control module 1000 can be configured to maneuver the robot 10 about afirst area while the robot 10 is in a cleaning mode. In the cleaningmode, the robot 10 can be redirected in response to detecting a gatewaymarking emission (e.g., from a beacon). In addition, the control module1000 can be configured to maneuver the robot 10 through a gateway intothe second bounded area while in a migration mode.

In some implementations, the control module 1000 is configured to movethe robot 10 in a first bounded area in the cleaning mode for a presettime interval. When the present time interval elapses, the controlmodule 1000 can move the robot 10 in a migration mode. While inmigration mode, the controller 1000 can direct the wheel modules 500,501 to maneuver the robot while substantially suspending the wetcleaning process. In some implementations, the migration mode can beinitiated when the omni-directional receiver 410 encounters the gatewaymarking emission a preset number of times.

Wall Follower

Dust and dirt tend to accumulate at room edges. To improve cleaningthoroughness and navigation, the robot 10 can follow walls. Additionallyor alternatively, the robot 10 can follow walls as part of a navigationstrategy (e.g., a strategy to promote full coverage). Using such astrategy, the robot can be less prone to becoming trapped in smallareas. Such entrapments could otherwise cause the robot to neglectother, possibly larger, areas.

Using a wall follower, the distance between the robot and the wall issubstantially independent of the reflectivity of the wall. Suchconsistent positioning can allow the robot 10 to clean withsubstantially equal effectiveness near dark and light colored wallsalike. The wall follower includes a dual collimination system includingan infrared emitter and detector. In such a collimination system, thefield of view of the infrared emitter and detector can be restrictedsuch that there is a limited, selectable volume where the cones ofvisibility intersect. Geometrically, the sensor can be arranged so thatit can detect both diffuse and specular reflection. This arrangement canallow the wall following distance of the robot 10 to be preciselycontrolled, substantially independently of the reflectivity of the wall.The distance that the robot 10 maintains between the robot and the wallis independent of the reflectivity of the wall.

Referring to FIGS. 4 and 23A-B, the robot 10 includes a wall followersensor 310 disposed substantially along the right side of the bumper300. The wall follower sensor 310 includes an optical emitter 312substantially forward of a photon detector 314. In some implementations,the position of the wall follower sensor 310 and the optical emitter 312can be reversed such that the wall follower sensor 310 is substantiallyforward of the optical emitter 312.

The emitter 312 and detector 314 are arranged in respective collimatortubes 316, 318, which can be defined by the bumper 300 or defined by ahousing mountable to the bumper 300. The collimator tubes 316, 318 arespaced closely together in a near-parallel oriention such that the fieldof emission of the emitter 312 intersects the field of view of thedetector 314 at a distance forward of the wall follower sensor (e.g.,about 1 cm to about 10 cm). As compared to wall follower sensors used onsome slower moving robots in which the emitter and detector are aimeddirectly at the wall, the near-parallel orientation of the emitter 312and the detector 314 results in an intersection zone that is bothfarther away and deeper for a given separation between the emitter 312and the detector 314. In some implementations, the angle formed betweenthe field of emission of the emitter 312 and the field of view of thedetector 314 is between about 10 degrees and 30 degrees (e.g., about 20degrees). Angles within this range result in a monotonic relationshipbetween the angle to the wall and the signal strength. In someimplementations, the respective collimators of the emitter and thedetector are angled toward one another. In some implementations, theangles of the respective collimators can change as the forward speed ofthe robot changes.

The near-parallel orientation of the optical emitter 312 and photondetector 314 can allow the robot 10 to follow the wall within a shortdistance of the wall. As compared to an orientation in which thecollimator of an emitter and the collimator of a detector aresubstantially angled toward each other, the near-parallel orientation ofthe optical emitter 312 and the photon detector 314 can result in a morelinear relationship between the distance from the wall and signalstrength.

FIG. 23B shows a schematic of the operation of the wall follower sensor310. The emitter 312 can emit a signal 320 toward wall 319. The wall 319reflects the signal such that a reflected signal 320′ scatters from thewall in various different directions. At least a portion of thereflected signal 320′ reflects back toward the field of view of thedetector 314. The detection of the reflected signal 320′ within thefield of view of the detector generates a signal to the controller 1000.In some implementations, the controller 1000 uses the signal to controlthe distance between the robot 10 and the wall 319.

Referring to FIG. 24, the control module 1000 can include logic thatcontrols wheel modules 500, 501 in response to signals detected by thewall follower sensor 310 to control the movement of the robot 10 at asubstantially parallel fixed distance from the wall. The wall followersensor 310 can modulate 350 signals from the emitter and detect signalsfrom the detector (e.g., as described above) until a reflection isdetected 352. A wall is then next to the robot and the control module1000 causes the robot to turn away 354 from the wall and then turn back356 until a reflection (the wall) is again detected 358. By continuouslydecreasing the radius of curvature of the robot 360, the path of therobot along the wall is made smoother. Additionally or alternatively,the controller 1000 can steer the robot 10 to maintain a substantiallyconstant analog value of the detected signal which can result in amaintaining the robot at a substantially constant distance from the wallas the robot follows the wall.

In addition to or in the alternative to detecting signals emitted by theoptical emitter 312, the photon detector 314 can be used as a receiverfor other signals. For example, the photon detector 314 can be used asan infrared port for receiving serial data transmission. Such transferof data through the photon detector 314 can reduce the need for cableports that can be difficult to seal and can act as water leak paths whennot in use. In some implementations, the control module 1000 can swapthe photon detector 314 between a wall following mode and a datatransfer mode. For example, when the control module 1000 detects thatthe robot 10 is not moving (e.g., through voltage and current signalsreceived from the wheel modules 500, 501), the control module 1000 canmonitor the photon detector 314 for a data transfer character. Upondetecting a data transfer character, the control module 1000 can switchthe photon detector 314 to a data transfer mode in which data can betransferred through the photon detector as described above. Additionallyor alternatively, upon detecting the data transfer character, thecontrol module 1000 can switch between an internal wireless serial port(e.g., a BLUETOOTH wireless serial port) to an external wall followerserial port without specific commands or requiring a switch button. Thecontrol module 1000 can prevent the robot 10 from moving until the datatransfer is complete. For example, the control module 1000 can refuse tomove the wheel modules 500, 501 during a state in which the wallfollower sensor 310 is enabled as a serial port (e.g., when the robot ispowered on but not cleaning). In certain implementations, when thecontrol module 1000 detects that the robot is moving, the control module1000 will ignore the data transfer character such that the controller1000 will not receive software updates while the robot 10 is in motion.

While the wall follower has been described

Bump Sensors

Bump sensors can be used to detect if the robot physically encounters anobstacle. Bump sensors can use a physical property such as capacitanceor physical displacement within the robot to determine the robot hasencountered an obstacle.

Referring to FIG. 7, the chassis 100 carries a right bump sensor 330 anda left bump sensor 332 substantially along a forward portion of thechassis 100. The bump sensors 330, 332 are substantially uniformlypositioned on either side of the fore-aft axis 22 and are positioned atsubstantially the same height along the center vertical axis 20. Asdescribed above, bumper 300 is attached to chassis 100 by hinges 110such that the bumper 300 can move a distance rearward along the fore-aftaxis 22 if the bumper 300 encounters an obstacle. In the absence of abump, the bumper 300 is hingedly supported on the chassis 100 at a shortdistance substantially forward of each bump sensor 330, 332. If thebumper 300 is moved rearward (e.g., through an encounter with anobstacle), the bumper 300 can press on one or both bump sensors 330, 332to create a bump signal detectable by the control module 1000.

In response to the detected bump signal, the control module 1000 cannavigated away from the bump. For example, the control module 1000 canmove the robot 10 backwards. In some implementations, the bumper 300 canmove transversely in response to a bump such that the bump sensors 330,332 can be used to determine the directionality of the bump. Forexample, if the bumper 300 encounters an obstacle on the right side, thebumper 300 can move transversely to the left to come into contact withthe right bump sensor 330. If the control module 1000 detects a signalfrom the right bump sensor 330 but does not detect a signal from theleft bump sensor 332, the control module 1000 can initiate an escapebehavior that will move the robot toward the left, away from the sensedbump condition. In an analogous example, the control module 1000 cannavigate the robot 10 away from a bump detected on the left side of therobot 10.

In some implementations, the control module 1000 can interrupt acleaning routine (e.g., stop the application of liquid to the cleaningsurface) upon activation of one or both of the bump sensors 330, 332and, additionally or alternatively, resume the cleaning routine uponcompletion of an escape routine. In certain implementations, bumpsensors can detect the amount of mechanical shock encountered by thebumper such that a control module can stop the cleaning routine if thedetected shock is above a threshold value (e.g., a shock indicating thatthe robot has fallen off of a surface).

For the purposes of illustration and explanation, the right bump sensor330 is described in detail below. The left bump sensor 332 includesfeatures analogous to the right bump sensor 330 and is identical to theright bump sensor 330 unless otherwise indicated.

Referring to FIGS. 25 and 26, the bump sensor 330 includes a sensor body340, a cone 342 supported on a surface of the sensor body 340, and abumper switch PCB 346 held on a surface of the sensor body 340substantially opposite to the surface supporting the cone 342. Thesensor body 340 includes overlapping regions 347 configured to extendaround edge regions of the bumper switch PCB 346 to hold the bumperswitch PCB 346 substantially in place. The overlapping regions 347 caninclude a small amount of adhesive to hold the bumper switch PCB 346 inplace. The bumper switch PCB 346 carries an electric circuit and isconfigured for electrical communication with the controller module 1000.

The cone 342 includes a wide end 341 and a narrow end 343 and defines afrusto-conical cavity therebetween. The wide end 341 is supported awayfrom the sensor body 340. In use, the bumper 300 contacts the wide end341 when upon encountering an obstacle. A conductive pill 348 isdisposed along the narrow end 343 of the cone 342. The conductive pill348 can be carbon and, additionally or alternatively, formed in theshape of a puck.

The sensor body 340 includes a resilient region 344 that forms adome-shaped cavity extending from the sensor body 340. The resilientregion 344 supports the narrow end of a cone 342, with the wide end ofthe cone 342 extending away from the resilient region 344. At least aportion of the conductive pill 348 extends into the dome-shaped cavityformed by the resilient region 344 at a distance (e.g., at least about 2mm) from the bumper switch PCB.

The resilient region 344 is configured to flex toward the sensor body340 in response to pressure exerted on the wide end 341 of the cone 342such that conductive pill 348 contacts the bumper switch PCB 346, actingas a mechanical switch to complete the circuit carried on the bumperswitch PCB 346 (e.g., generate a signal to controller module 1000). Insome implementations, the cone 342 and/or the resilient region 344absorb some of the mechanical shock generated by contact with the bumper300 and, thus, reduce the force transmitted from the conductive pill 348to the bumper switch PCB 346. Such deformation of the cone 342 canreduce the likelihood that the mechanical shock of encountering anobstacle will damage (e.g., fracture) the bumper switch PCB 346.

Upon removal of pressure from the wide end of the cone 342, theresilient region 344 returns the cone 342 substantially to its initialorientation away from the bumper switch PCB 346. With the conductivepill 348 positioned away from the bumper switch PCB 346, the circuitcarried by the bumper switch PCB 346 is incomplete and no signal is sentto the control module 1000.

In some implementations, the base 340 and cone 342 are integrally formedof silicone. In certain implementations, the silicone is molded over theconductive pill 348 to hold the conductive pill 348 substantially inplace on the narrow end 348 of the cone 342.

Cliff Sensor

Cliff sensors can be used to detect if a portion (e.g., a forwardportion) of the robot has encountered an edge (e.g., a cliff). Cliffsensors can use an optical emitter and photon detector pair to detectthe presence of a cliff. In response to a signal from a cliff detector,the robot can initiate any of various different cliff avoidancebehaviors. Referring to FIG. 27, bumper 300 includes a left cliff sensor360, a center cliff sensor 362, and a right cliff sensor 364, eachdisposed along a lower portion of the bumper 300. The cliff sensors 360,362, 364 substantially uniformly spaced from one another and each sensor360, 362, 364 is aimed downward toward the surface. Center cliff sensor362 is arranged near the center of the bumper 300, substantially belowthe fill door 304.

Referring to FIG. 28, left and right cliff sensors 360, 364 are arrangednear respective right and left ends of the bumper 300 and positionedsubstantially forward of and substantially aligned with wheels 504 and505, respectively. Such positioning of the right and left cliff sensors360, 364 can allow the robot 10 to travel at high rates of forward speed(e.g., about 200 mm/s to about 400 mm/s) while allowing the robot 10sufficient time to detect a cliff event and successfully respond to thedetected cliff event (e.g., overcoming the forces of forward momentum tostop before one or more wheels goes over the cliff). For example, upondetecting a cliff event at cliff sensor 360, wheel 504 can remain incontact with the surface and can provide traction and rearward thrustduring an escape procedure. In implementations in which the robot weighsless than 2 kg fully loaded with cleaning liquid and travels at amaximum forward rate of about 200 mm/s to about 400 mm/s (e.g., about300 mm/s), cliff sensors 360, 364 are positioned between about 50 mm toabout 100 mm substantially forward of respective wheels 504, 505.

Referring to FIG. 29, the cliff sensors 360, 362, 364 each include ahousing 366 defining an emitter collimator tube 368 and a detectorcollimator tube 370, each angled substantially toward one another. Anoptical emitter 372 is arranged substantially within the emittercollimator tube 368, and a photon detector 374 is arranged substantiallywithin the detector collimator tube 370. Optical emitter 372 generates asignal 376 toward the surface 378. The signal 376′ reflects off of thesurface 378 back toward the detector collimator tube 370 and is detectedby the photon detector 374.

Referring to FIG. 30, each cliff sensor 360, 362, 364 modulates theemitter at a frequency of several kilohertz and detects 380 any signalfrom the detector, which is tuned to that frequency. When a signal isnot output by the detector, 382, the expected surface is not present andno overlap is detected. In response, an avoidance algorithm is initiated384 to cause the robot to avoid the cliff. When a reflected signal isdetected, processing continues 380.

In some implementations, cliff sensors 360, 362, 364 can be used todetect stasis of the robot 10. The wetting element 204 of the robot is apassive element and, therefore, does not substantially interfere withthe signal processing of the cliff sensors 360, 362, 364. Thus, forexample, the controller 1000 can move the robot 10 back and forth in awiggle motion as the robot 10 moves along the surface. Withoutsubstantial interference from other components of the robot 10, eachcliff sensor 360, 362, 364 can detect small variations in the reflectedsignal 376′, the variations corresponding to variations in the surfaceas the robot 10 moves across the surface (e.g., in a straight linemotion, in a turning motion, in a wiggle motion). Absence of variationsin the reflected signal 376′ is an indication that the robot 10 is in astuck condition.

Stasis Sensor

A stasis sensor can be used to detect whether or not the robot is infact moving. For example, a stasis sensor can be used to detect if therobot is jammed against an obstacle or if the drive wheels aredisengaged from the floor, as when the robot is tilted or becomesstranded on an object. In a wet cleaning application, a stasis sensorcan detect whether the wheels are slipping on a cleaning liquid appliedto the surface. In such circumstances, the drive wheels may spin whenthe mobile robot applies power to them, but the robot is not moving.

Referring to FIGS. 3, 31, a stasis sensor 540 is carried by the chassis100, inward of the right wheel module 500. The stasis sensor 540 issubstantially aligned the transverse axis 500 and is in non-load bearingcontact with the surface. FIG. 31 shows the stasis sensor 540 carried onthe chassis 100 with the wheel module 500 removed. The stasis sensor 540rotates about the transverse axis 23 as the robot 10 moves.

Referring to FIG. 32, the stasis sensor 540 includes a stasis wheel 542defining a center bore 543 and defining a magnet recess 548 offset fromthe center bore 543. A hub 544 is substantially aligned with the centerbore 543 and configured to secure the stasis wheel 542 rotatably to awheel housing and allow the stasis wheel 542 to spin freely in responseto frictional contact with the surface or floor during robot movement. Amagnet 546 is arranged (e.g., press fit) into the magnet recess 548.

In use, the stasis sensor 540 rotates and the magnet 546 activates areed switch in the robot. The activation of the reed switch creates asignal detectable, for example, by the controller 1000. In thisconfiguration, the stasis sensor 540 produces one signal pulse perrotation of the stasis wheel. The signal produced by the stasis sensor540 can be used for stasis detection and/or odometry. In someimplementations, each drive wheel includes a stasis sensor. In suchconfigurations, the controller 1000 can determine motion of the robotbased on differences in the outputs from each senor. For example, thecontroller 1000 can determine whether and in which direction the robotis turning.

While the stasis sensor has been described as including a magnet thatactivates a reed switch, other implementations are possible. In someimplementations, the stasis sensor can include a breakbeam arrangementin which an optical emitter and photo detector pair are positionedsubstantially across the stasis sensor. As the stasis sensor rotates theemitter/detector pair can detect breaks in the beam caused by therotating stasis wheel.

In some implementations, the stasis wheel can include alternating lightsections and dark sections. An optical sensor can be positioned near thestasis wheel to detect transitions from the light section to the darksection (and vice versa) as the bi-colored wheel spins. By monitoringthe contrast between the detection of the light and dark sections of thebi-colored wheel, the optical sensor can output a signal to thecontroller indicating that the bi-colored wheel has become too dirty orobscured to be useful in motion, speed, or stasis detection, forexample. In response, the controller can transition to another stasisdetection system.

In certain implementations, a stasis sensor includes a drive motorcurrent sensor which monitors the current (hereinafter the “drivecurrent”) drawn by a drive motor that turns one or more of the drivewheels for propelling the robot. The drive motor current sensor and thedrive motor can both be carried by a drive wheel module. When the drivecurrent is higher than a threshold value, the stasis sensor determinesthat the robot is in a stasis condition. When the drive current is lowerthan a threshold value, the stasis sensor determines that the load onthe wheels is too low (e.g., the wheels are slipping).

Referring to FIG. 33, in certain implementations, stasis can be detectedusing a wiggle sensor 550. The wiggle sensor 550 includes a housing 552having two surfaces 556, 554 sloped toward each other and define asubstantially v-shaped cavity 555 in the housing 552. The housing 552includes an optical emitter 558 and a photo detector 560 arranged oneither side of the v-shaped cavity. The optical emitter 558 isconfigured to send a signal toward the photo detector 560, and the photodetector 560 is configured to sense the signal. When the controller 1000moves the robot 10 in a wiggle motion, a ball (not shown) moves up anddown the v-shaped cavity in response to the wiggle motion. The movementof the ball in the v-shaped cavity is detected as an interruption of thesignal passing between the optical emitter 558 and the photo detector560. Such an interruption is indication that the robot 10 is moving inresponse to the wiggle motion. If the signal passing between the opticalemitter 558 and the photo detector 560 remains uninterrupted during awiggle motion, the controller 1000 interprets the uninterrupted signalas a stasis condition.

The controller 1000 can use an algorithm to transition from a firststasis detection system to a second stasis detection system. Thetransition can be unitary (switching entirely and immediately), or itcan be gradual in degree and/or time (e.g., by applying a confidencecoefficient for the first stasis detection system and/or the secondstasis detection system). The controller 1000 can evaluate inputs fromboth stasis detection systems simultaneously, integrating the evaluatedinputs according to an integration equation in accordance with thenature of the first and second stasis detection systems.

Power Module/Interface Module

The power module 1200 delivers electrical power to all of the majorrobot subsystems. The power module 1200 includes a self-contained powersource releasably attached to the chassis 100, e.g., a rechargeablebattery, such as a nickel metal hydride battery, or the like. Inaddition, the power source is configured to be recharged by any ofvarious different recharging elements and/or recharging modes. In someimplementations, the battery can be replaced by a user when the batterybecomes discharged or unusable. The controller 1000 can also interfacewith the power module 1200 to control the distribution of power, tomonitor power use and to initiate power conservation modes as required.

The robot 10 can include one or more interface modules 1700. Eachinterface module 1700 is attached to the chassis 100 and can provide aninterconnecting element or port for interconnecting with one or moreexternal devices. Interconnecting elements are ports can be accessibleon an external surface of the robot 10. The controller 1000 can alsointerface with the interface modules 1700 to control the interaction ofthe robot 10 with an external device. In particular, one interfacemodule element can be provide for charging the rechargeable battery viaan external power supply or power source such as a conventional AC or DCpower outlet. The interface module for charging the rechargeable batterycan include a short-circuit loop that will prevent the rechargeablebattery from taking charge if there is water in the charge port of therobot 10. In some implementations, the rechargeable battery includes afuse that will trip if there is water in the battery recharging path.

Another interface module element can be configured for one or two waycommunications over a wireless network and further interface moduleelements can be configured to interface with one or more mechanicaldevices to exchange liquids and loose particles therewith, e.g., forfilling a cleaning fluid reservoir.

Active external devices for interfacing with the robot 10 can include,but are not limited to, a floor standing docking station, a hand heldremote control device, a local or remote computer, a modem, a portablememory device for exchanging code and/or date with the robot 10 and anetwork interface for interfacing the robot 10 with any device connectedto the network. In addition, the interface modules 1700 can includepassive elements such as hooks or latching mechanisms for attaching therobot 100 to a wall for storage or for attaching the robot to a carryingcase or the like.

In some implementations, an active external device can confine the robot10 in a cleaning space such as a room by emitting a signal in a virtualwall pattern. The robot 10 can be configured to detect the virtual wallpattern (e.g., using an omni-directional receiver as described above)and is programmed to treat the virtual wall pattern as a room wall sothat the robot does not pass through the virtual wall pattern. Such aconfiguration is described in U.S. Pat. No. 6,690,134 by Jones et al.,entitled Method and System for Robot Localization and Confinement, theentire disclosure of which is herein incorporated in its entirety.

In some implementations, an active external device includes a basestation used to interface with the robot 10. The base station caninclude a fixed unit connected with a household power supply, e.g., anAC power wall outlet and/or other household facilities such as a watersupply pipe, a waste drain pipe and a network interface. The robot 10and the base station can each be configured for autonomous docking andthe base station can be further configured to charge the robot powermodule 1200 and to service the robot in other ways. A base station andautonomous robot configured for autonomous docking and for rechargingthe robot power module are described in U.S. patent application Ser. No.10/762,219, by Cohen, et al., filed on Jan. 21, 2004, entitledAutonomous Robot Auto-Docking and Energy Management Systems and Methods,the entire disclosure of which is herein incorporated by reference inits entirety.

Other robot details and features combinable with those described hereinmay be found in the following U.S. patent application filed May 9, 2008,entitled “COMPACT AUTONOMOUS COVERAGE ROBOT” having assigned Ser. No.12/118,117, the entire contents of the aforementioned application ishereby incorporated by reference.

What is claimed is:
 1. An autonomous robot comprising: a body movable in a forward direction over a cleaning surface; a drive system comprising a right drive wheel and a left drive wheel, the right drive wheel and the left drive wheel being rotatable about at least one transverse axis approximately orthogonal to the forward direction; a replaceable scrubbing pad comprising: a first arcuate edge having an end proximate the right drive wheel, the first arcuate edge extending from the end of the first arcuate edge toward a fore-aft axis of the autonomous robot, the first arcuate edge being substantially parallel to and adjacent to a first portion of an outer perimeter of the autonomous robot toward the fore-aft axis, a second arcuate edge having an end proximate the left drive wheel, the second arcuate edge extending from the end of the second arcuate edge toward the fore-aft axis of the autonomous robot, the second arcuate edge being substantially parallel to and adjacent to a second portion of the outer perimeter of the autonomous robot, and a central region between the first arcuate edge and the second arcuate edge, the central region being adjacent to the outer perimeter of the autonomous robot; a driving module for moving the replaceable scrubbing pad with respect to the body; a liquid storage tank that stores a liquid; a liquid applicator that introduces the liquid to the replaceable scrubbing pad; and a vacuum assembly that generates suction to draw debris from the cleaning surface through an aperture in the autonomous robot.
 2. The autonomous robot according to claim 1, further comprising hinge features on the body, and the replaceable scrubbing pad comprises a baseplate configured to engage with the hinge features on the body.
 3. The autonomous robot according to claim 1, wherein the replaceable scrubbing pad comprises a baseplate configured for removable attachment to the autonomous robot via a snap engagement.
 4. The autonomous robot according to claim 1, wherein the replaceable scrubbing pad comprises a baseplate removable from the autonomous robot.
 5. The autonomous robot according to claim 1, wherein the driving module is configured to rotate the replaceable scrubbing pad.
 6. The autonomous robot according to claim 1, wherein the driving module is configured to vibrate the replaceable scrubbing pad.
 7. The autonomous robot according to claim 1, further comprising a handle positioned on the autonomous robot, the handle configured to be movable to a position flush with a top portion of the body and to be biased toward the position.
 8. The autonomous robot according to claim 7, wherein the handle pivots about a transverse axis extending along a center of gravity of the autonomous robot.
 9. The autonomous robot according to claim 1, wherein the autonomous robot is configured to move over cleaning paths according to three operational movement patterns.
 10. The autonomous robot according to claim 9, wherein at least one of the three operational movement patterns comprises repeated alternating right and left turns.
 11. The autonomous robot according to claim 9, wherein at least one of the three operational movement patterns comprises a back and forth movement.
 12. The autonomous robot according to claim 1, wherein a maximum height of the autonomous robot is less than 10 cm.
 13. The autonomous robot according to claim 1, further comprising: a battery; and a charging interface for electrically connecting an external power source to the battery for charging.
 14. The autonomous robot according to claim 1, further comprising a wireless communication interface for wirelessly receiving control instructions from one or more devices.
 15. The autonomous robot according to claim 1, further comprising a bumper configured to preclude the autonomous robot from mounting a carpeted floor.
 16. The autonomous robot according to claim 15, wherein the bumper has a ground clearance between 2-5 mm.
 17. The autonomous robot according to claim 1, wherein lateral portions of the body form a substantially circular cross-section of the autonomous robot.
 18. The autonomous robot according to claim 1, further comprising a baseplate attachable to the body of the autonomous robot, the baseplate configured to be carried on a bottom portion of the body.
 19. The autonomous robot according to claim 18, wherein the replaceable scrubbing pad is removably attachable to the baseplate.
 20. The autonomous robot according to claim 18, wherein the first arcuate edge of the replaceable scrubbing pad extends along a first corresponding arcuate edge of the baseplate, and the second arcuate edge of the replaceable scrubbing pad extends along a second corresponding arcuate edge of the baseplate.
 21. The autonomous robot according to claim 1, wherein the autonomous robot has a substantially cylindrical shape.
 22. The autonomous robot according to claim 1, wherein the driving module comprises an ultrasound emitter to generate a scrubbing action of the replaceable scrubbing pad.
 23. The autonomous robot according to claim 1, further comprising an extension element positioned along a forward portion of the autonomous robot and extending beyond the outer perimeter of the autonomous robot, the extension element configured to contact the cleaning surface to direct debris toward the aperture in the autonomous robot.
 24. The autonomous robot according to claim 1, wherein the liquid applicator is configured to apply fluid by a dripping or a capillary action to the replaceable scrubbing pad.
 25. The autonomous robot according to claim 1, wherein a linear edge of the replaceable scrubbing pad proximate the left drive wheel or the right drive wheel extends along a transverse axis.
 26. The autonomous robot according to claim 25, wherein the end of the first arcuate edge is connected to the linear edge.
 27. The autonomous robot according to claim 1, further comprising: a sensor system; and a controller configured to navigate the autonomous robot in response to one or more signals generated by the sensor system, the sensor system comprising a cliff sensor, a wall follower sensor, and a bump sensor.
 28. The autonomous robot according to claim 1, wherein the replaceable scrubbing pad has a width of at least a transverse distance between the left drive wheel and the right drive wheel. 